Oil change conundrum
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?
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
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
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
Regards
Pat
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RE: Oil change conundrum
RE: Oil change conundrum
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
RE: Oil change conundrum
Thanks for the confirmation, I feel safe ignoring the mileage and driving it further.
RE: Oil change conundrum
I have switched over to Valvoline full synthetic since Mobil 1 was reformulated.
Mike Halloran
Pembroke Pines, FL, USA
RE: Oil change conundrum
RE: Oil change conundrum
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.
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
RE: Oil change conundrum
Why do you change it, then? Feeling guilty?!
RE: Oil change conundrum
rmw
RE: Oil change conundrum
RE: Oil change conundrum
RE: Oil change conundrum
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RE: Oil change conundrum
Regards
Pat
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RE: Oil change conundrum
RE: Oil change conundrum
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
Regards
Pat
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RE: Oil change conundrum
RE: Oil change conundrum
RE: Oil change conundrum
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RE: Oil change conundrum
Rod
RE: Oil change conundrum
Don't you use your old race oil in a beater that burns oil anyway.
Regards
Pat
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RE: Oil change conundrum
Rod
RE: Oil change conundrum
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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
Rod
RE: Oil change conundrum
RE: Oil change conundrum
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
I always find that the oil seems to go down the storm drain better after midnight
rmw
RE: Oil change conundrum
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
RE: Oil change conundrum
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
FYI: Vehicles equipped with oil life monitors can not tell the difference in oil quality.
NOTE: Regardless of remaining oil life, GM recommends oil be changed at least annually.
RE: Oil change conundrum
see that the NEW formatting tools are not going to waste.RE: Oil change conundrum
Rod
RE: Oil change conundrum
RE: Oil change conundrum
Regards
Pat
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RE: Oil change conundrum
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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
RE: Oil change conundrum
RE: Oil change conundrum
Rod