INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Oil change conundrum3

## Oil change conundrum

(OP)
I recently took my '86 Porsche 944 on a 3500-mile cross-country trip.  Before the trip, I changed the oil & filter (Castrol GTX 20w50 "conventional" with a NAPA Gold filter made by Wix).

I made the trip up and back in 2.5 days each way, approx. 1500 miles each way, and drove about 500 miles at my destination over a period of a week.  This was in August, temps were pretty moderate, under 90 F. the whole time, above 70 at night. This car has a water-to-oil cooler.

Basically, each day of travel I had one "cold" start, and several warm starts.  I was cruising at 2,500 RPM (60 mph).

So... "conventional wisdom" would say I have 3,500 miles on my oil, it's time for a change, right?  I don't think so, but I can see things both ways.

Compared to driving around town (suburban cycle) for 3,500 miles, I had perhaps 1/100th the number of cold starts;  and I have about 30 hours driving time on the oil, vs. 125 - 150 hours. In terms of time, this mileage occured in 10 days vs. 6 months that it would normally take me to accumulate that many miles.

The other side of the coin is, I have 3,500 miles on the oil.  I suppose there are going to be a certain number of wear particles generated whenever an engine is running, but again, the amount generated at a relatively constant 2,500 RPM vs. constant cycling in traffic is bound to be much less.

I think it would be a waste to drain this oil.  What say you?

### RE: Oil change conundrum

Many years ago, I changed oil religiously at 3000 miles or so, and got decent engine life even from cheap oil.

I started using extended drain intervals when I changed to synthetic oil, which seemed to work just fine for up to 15,000 miles.  An engine that I ran to a 20,000 mile change, on synthetic oil, died about five years later because the pickup fell off, but I don't think that was the oil's fault.

In your case, good quality dino oil hardly used, I'd run it for a while longer, probably to the engine manufacturer's change interval.  ... but you're already feeling guilty, aren't you?

Mike Halloran
Pembroke Pines, FL, USA

### RE: Oil change conundrum

(OP)

#### Quote:

... but you're already feeling guilty, aren't you?

Yes! My inclination is to run it to 4 months or 6,000 miles; in other words, discount the trip mileage. By then it will be colder outside and I like to change more often based on (truly) cold starts (condensation potential).

I didn't state it, but the car has 96k miles and runs like new after a healthy infusion of greenbacks, mostly for normal wear parts.  I averaged 29.9 mpg overall on the trip, too.

### RE: Oil change conundrum

I'd keep driving.
Your oil has 3,500 miles on it, in that it traveled 3,500 miles.
It likely has quite a bit fewer rpm/hours on it than you  would typically have  after 3,000 miles.
AND, as you noted. far fewer cold starts, and just fewer starts.
far less cold operation, idling etc.
That oil has had it easy

Yep, drive on!

### RE: Oil change conundrum

I use Mobil 1 and leave it in there for 5 times that long or more and still get good engine life, and my cars get a hard life with all sorts of conditions from red lining it through the gears through winding hilly roads to stop start city driving.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules

### RE: Oil change conundrum

Isn't the owner's manual recommendation for that vintage Porsche 5000 miles for a non-turbo? And that was the days back when maintenance schedules may have had a dealer service agenda, before folks accuse manufacturers of just wanting to survive the free maintenance lease period?

2
if you really want to know the answer, spend $30 for an oil analysis now, then run a while longer (if analysis allows) and repeat until you've seen enough. If you wait long enough to do the first analysis, you can probably end the experiment conclusively after just two measurements ("almost there" and "just past"). ### RE: Oil change conundrum Isn't the street price for Castrol GTX and a Wix filter around$30?  Waste or not, it seems like a small price to pay for peace of mind.  Personally, I aim for 7500 miles with Mobil 1 and a Purolater Plus or Bosch Oil filter (whatever is on special for ~$30 at my local store). I say aim because it rained for the last two weekends so I'm close to 8,000 and hope to do it this weekend. ### RE: Oil change conundrum (OP)$30 is $30... I have 4 vehicles, if I applied the "better safe than worry" theory I'd be in a world of hurt. The 944 uses 6 liters, and a filter that's not in the bargain bins, so it does come out to about$30.  (The filter is very thoughtfully mounted upside down, too, great engineering there).

Thanks for the confirmation, I feel safe ignoring the mileage and driving it further.

### RE: Oil change conundrum

With a spin-on filter installed threaded side down, a prick punch will make it drain where you want it to.  ... mostly.

I have switched over to Valvoline full synthetic since Mobil 1 was reformulated.

Mike Halloran
Pembroke Pines, FL, USA

### RE: Oil change conundrum

for what it's worth, my '03 Mini Cooper was good for 20k to 25k miles between oil changes using Mobil 1 synthetic.  Oil analysis showed no parameters out of range, but TBN was getting close.

### RE: Oil change conundrum

(OP)

#### Quote:

for what it's worth, my '03 Mini Cooper was good for 20k to 25k miles between oil changes using Mobil 1 synthetic.  Oil analysis showed no parameters out of range, but TBN was getting close.

Unfortunately, that is more than 4 years of mileage on this car, because I just don't drive that much (not commuting, 4 vehicles to chose from, live where I can walk or ride my bicycle to almost everything).  In normal use, my oil concerns are more due to short trips.

#### Quote:

With a spin-on filter installed threaded side down, a prick punch will make it drain where you want it to.  ... mostly.

That's the theory anyway, in practice these filters seem to hold their charge until you get it tipped to a 45-deg angle right over the belts and wiring bundles...

One of my other vehicles is a lowly Chev S-10 w/2.2L 4-banger.  They very thoughtfully provided a plastic drain trough on the side of the engine that surrounds the filter base and drains off to a spot that is accessible.

### RE: Oil change conundrum

annual mileage on my two current vehicles, a scion xb and ford explorer, is 8k-10k.  I change the oil annually (Mobil 1 5w30 synth), and according to oil analysis it's not "used up" at that point.

### RE: Oil change conundrum

(OP)

#### Quote:

I change the oil annually (Mobil 1 5w30 synth), and according to oil analysis it's not "used up" at that point.

Why do you change it, then?  Feeling guilty?!

### RE: Oil change conundrum

If you are still on the fence, change the filter and add a quart and drive on for a while.

rmw

### RE: Oil change conundrum

no, it happens that I'm off of work for an extended period at the end of each year, so things like changing the oil in all of my engines seem less of a time drain.

### RE: Oil change conundrum

I wonder how many Prius/miles it takes to offset the petro dollars consumed in all the premature oil changes.

### RE: Oil change conundrum

depending on what's done with the reclaimed oil, probably not many.

### RE: Oil change conundrum

(OP)
I'm at a loss to understand how Valvoline is going to get almost a buck a quart more for re-refined/recycled "NextGen" oil than "virgin" oil.  Guilt?

### RE: Oil change conundrum

Properly re-refined instead of just filtered and topped up with extra additive I imagine has the advantage of starting with a much better feedstock than raw crude oil.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules

### RE: Oil change conundrum

When introduced the trade mags reported Valvoline was going to position NextGen at price parity to virgin oil.  But they don't control the retail price, so the markup may be going to the retailer's tils rather than the Ashland folks.

### RE: Oil change conundrum

(OP)

#### Quote:

Isn't the owner's manual recommendation for that vintage Porsche 5000 miles for a non-turbo? And that was the days back when maintenance schedules may have had a dealer service agenda, before folks accuse manufacturers of just wanting to survive the free maintenance lease period?

My face is red on this one.  I hadn't ever found the interval in any of the manuals, I relied on what I read in the many debates on oil quality and change intervals on Rennlist and elsewhere.  The Owner's Manual doesn't give an interval, just the viscosity, API Service, etc.  I dug thru all the paperwork some more and finally found the interval in the Warranty booklet.

After the first 7,500 miles (i.e., break-in) the recommended interval is 15,000 miles or one year!  No mention of synthetics to achieve this, either.  There are the usual caveats about racing or severe service.  I'm honestly shocked.

### RE: Oil change conundrum

various Moparz and Toyotae have had some sludge related horror stories that seem to indicate the factory may misjudge the change interval sometimes, but when Volvo embraced 5000 mile plus oil changes pretty early on it was easy for me to start stretching them out.

### RE: Oil change conundrum

Some years back when the price of mineral oil(no such thing as dino)went up, I stopped doing the 3000 mile change deal. Switched to synthetic and don't worry about it. It maybe 6k to 10k for a change now sometimes more. Except for the wifes subaru, just mineral oil there, hasn't had an oil change in years. But has clean oil all the time. What can I say its a good old subaru.

### RE: Oil change conundrum

It's always ~interesting" reading options when this topic comes up. You can basically do one of 3 things. Follow your own "best guess", follow the manufacturer's recommendations or do the analysis tests like ivymike has suggested. Of course, the analysis tests will give you real data while the other 2 will either have you changing the oil too soon or too late.

### RE: Oil change conundrum

I'll bet if you showed the data to a room full of 'experts', half would still tell you it's too soon and half would say too late.

### RE: Oil change conundrum

Why are you running 20W50?

### RE: Oil change conundrum

(OP)
Kevin, there are many reasons (you can Google it and find dozens of threads specific to 944's), but the primary one is that that is what Porsche says to use. The Castrol 20w50 also has a healthy amount of ZDDP etc.

### RE: Oil change conundrum

I was once totally anal about oil change/service intervals.  As I have gotten too old to worry as much, I now simply devote the month of June (once a year) to change oil....in everything except the race cars which they have their Wix racing (51515R) filters and ten quarts of Red Line oil changer every two events.  The rest, vintage, trucks, motor home and, cars get Castrol 20W-50 GTX.  The wife makes me take her Lincoln to the dealer which is fine by me. Changing oil in seven cars is a PITA, and taking 15 gal of used oil to be recycled is no fun, either.

Rod

### RE: Oil change conundrum

Yeah, Pat.  I did that for a while. Not now, no beaters left, gave them all away.  I've even cut back on most of my vintage car stuff.  I sold my '39 Buick, '59 Nash and '48 Norton. Still have my two pre war Fords and my race Mini.  Just cutting back a bit 'cause I'm just getting too old to keep it all up and running.  Now the used oil gets dumped at several parts houses since they, individually, will only accept five gallons at a time.  I have about twenty gallons out there right now.  Gotta get off my arse and do something about that...

Rod

### RE: Oil change conundrum

Why do they limit it?  I think they are making money selling it to the recycler.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

### RE: Oil change conundrum

Good question.  Trust that I have asked.  The only place that took all that I had (15 gal. at that time) was the Lube and Tune place.  Parts stores are just closer and if I would just dump it when a five gallon can was filled there would be no problem...I'm the problem in this scenario.

Rod

### RE: Oil change conundrum

(OP)
The local AutoZone told me it was a zoning thing; 5 gallon limit ensures it is a convenience for residential/consumer customers, which keeps it within their zoning classification.  Larger amounts put it in a class of commercial work that triggers some different zoning requirements, different fire prevention, etc.

### RE: Oil change conundrum

I read some long time ago that BMW's original service indicator system for their fuel injected engines cars took all sorts of inputs to calculate the oil change interval, quite a complicated process.

Then someone realised that just keeping tabs on the amount of fuel run through the engine amounted to just about the same thing.

My year 2000 BMW 325's oil changes were supposed to be about 15,000 miles but the service indicator on mine calculated about 18,000 miles, due to my style of driving, i.e. mainly 70 mph cruising on the motorways. Engine still in top condition after 12 years and 126,000 miles, Emissions test came out perfect on it's original engine, exhaust system, cat etc. The oil never got black, only became darker brown in colour. OE filters always used.

Just part-ex'd that car in yesterday(!) for a Volvo S40 D5 turbodiesel. Very torquey engine for a 2.4 litre but I don't think this one will be so benign, albeit the service intervals are also supposed to be 18K miles.

### RE: Oil change conundrum

Rod,

I always find that the oil seems to go down the storm drain better after midnight

rmw

### RE: Oil change conundrum

Yeah, we probably would be put in jail today for the stuff we did.
We moved around a lot in the 60's and 70's so we rented a lot of homes in various parts of the southwest.  First thing I did was to dig a pit under the trash can...that's where all the drain oil went.
With our first home in Long Beach there was a storm drain at the junction of two alleys behind my house...coming back from a race weekend the motor home dump accidentally coincided with that particular storm drain.
I'm mister goody two shoes these days.  I'm very conscious about recycling and environmental issues.  Gettin' old, I guess.

Rod

### RE: Oil change conundrum

plus a lot of places will take (back) drained oil and some other fluids for free.  Walmart, in walmart containers, no questions asked. Autozone and Advanced auto. Probably lots of others

### RE: Oil change conundrum

I asked the 'lubentune' guy and all he said was "It's very profitable"...When they are not too busy, he will take all that I have...

I did manage to get three of my five gallon jugs emptied before I lost interest.  I'll probably procrastinate  until all five cans are full again...Why do today what you can put off 'till tomorrow?

Rod

### RE: Oil change conundrum

I see that the NEW formatting tools are not going to waste.

### RE: Oil change conundrum

I bought my wife a new 328IT for our 50th wedding anniversary. We were planning a trip but health issues made the new car the best option. Now this 2011 BMW has NO dipsticks. None. The oil level, trans level, brake fluid level, water level... all managed by the electronics. Hell, even the tire pressure is monitored by the damn computer. It has 360 degree radar and a 'monitored' speed control that won't let you get to close to another car without first a warning and then reduction in throttle. OIL CHANGE? The computer figures that out by how hard you drive the car and notify the 'car' and the dealer when oil change is due. At present it says we need our FIRST oil change in 1300 miles on July, 2013. Okay, where does that leave the old farts like me? And Ross, and Pat and, ... oh well!

Rod

### RE: Oil change conundrum

Dipstick = Smartphone??

### RE: Oil change conundrum

I don't think I'll ever be able to buy a new car again. It's not just these maintenance and "nanny" issues, they all have onboard "black boxes" that continuously record speed, throttle position, ABS, etc. Then in the case of a serious accident, your car's black box is pulled and used as testimony against you in court. Maybe if I marry it then the testimony can be blocked.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

### RE: Oil change conundrum

(OP)
My past experiences trying to buy relatively common wear parts for a 8 or 8 yr old car, and finding they are no longer available, makes me wonder what kind of dealer support there will be for all the  electronic crap it takes for a car like that BMW. Personally, I'm watching for a clean '60's car with a wiring diagram that fits on one sheet.

### RE: Oil change conundrum

A not-old-enough-to-be-a-curmudgeon buddy used to say the only cars he'd ever own would have the key/ignition in the dash. At the time ( 1980s) that meant pre-steering/ignition interface lock etc that was mandated in the early '70s if not before.

### RE: Oil change conundrum

It's my wife's car. She loves it. Nuff said. I'm still driving the Dodge/Cummins one ton duelly I bought new in 1991 and it still gets 21/22 mpg at well over 300,000 miles. Repainted in 2001 and it has 'issues' with the headliner, otherwise it's as I bought it, all the hoses except belt, brakes and, tires are OEM. I just cannot see any use (for me, I don't even listen to the radio) for the computer. My son just "sent" a whole list of albums "to the car" for my wife's listening pleasure!

Rod

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!