reglar vs hight test gas
reglar vs hight test gas
(OP)
Is it cost effective to use regular gas on an engine that is rated for high test? Is there any documentation around?
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reglar vs hight test gas
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reglar vs hight test gasreglar vs hight test gas(OP)
Is it cost effective to use regular gas on an engine that is rated for high test? Is there any documentation around?
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RE: reglar vs hight test gas
Rod
RE: reglar vs hight test gas
id say try it for a while and see.
also watch your tire pressures and keep clean oil and clean air filters, they seem to matter the most.
RE: reglar vs hight test gas
As for the oil filter, I don't see a correlation to fuel economy either excepting accelerated wearout of the engine leading to increased blowby, but that would be a long term process and difficult to quantify.
Tire pressures & driving style (especially cruising speed, in long distance driving) are the 2 biggies under the owner/driver's control. Gasoline octane rating typically has little or no effect on fuel economy since most driving is at part load, but will have an effect on maximum power, cost of fuel of course, and possibly engine longevity depending how well the engine management handles lower octane (probably not a concern in <10 year old cars).
RE: reglar vs hight test gas
For a start, many knock sensors don't work at full throttle/high speed, there is too much noise, so you are working off the spark table, not the knock sensor.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: reglar vs hight test gas
Presuming the engine can compensate to avoid damage (many modern engines can compensate) the economy issue comes down to several variables mostly mentioned or hinted at above.
The factors are:-
Effect on timing due to knock sensor.
Throttle position and it's effect on a:f ratio.
Price difference for the different fuels.
Ambient temperature.
Energy content of different fuels (ethanol containing fuels have low energy)
This link has a lot of info on fuels.
http:/
Regards
eng-tips, by professional engineers for professional engineers
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RE: reglar vs hight test gas
Add a 2005 Mini Cooper (naturally aspirated) to the list. When I had mine, it would take a ~20% hit on fuel economy if I put in 87 octane fuel. At the time $0.20/gal was 10% of fuel cost, so putting in premium was a net savings... that's part of what drove me to buy a pickup truck as a replacement - the fuel costs per month were about the same (ford ranger at 23-27mpg vs mini at 27-31).
RE: reglar vs hight test gas
Clean oil? Next you will be telling me that a clean car gets better mileage than a dirty one....hmmmmm? Could be, if it is an indication of the condition of the mech bits and pieces.
So far, IMO, all this discussion is academic. I don't see any fewer SUV's going 80+. I don't see an increase in the local high school kids 'walking' or (gag) riding a bicycle. I don't see a rash of new motorcycles as I did in 1973/4. In fact, it appears to be "situation normal" (for Socal, anyway). Speaking of Socal, I hear that there is at least one "hypermiler" club in the San Fernando Valley, if your interested.
Rod
RE: reglar vs hight test gas
RE: reglar vs hight test gas
I had an 84 Capri (3.8L V6) with +100Kmi that consumed noticeable oil and would ping enthusiastically on hard acceleration on 87 AKI gas. I filled it ca. half with 87 topped off with 93 to get about a 90 rating for the price of the 89 mid-grade and prevented the knock. I was a student at the time with no $$ or time for a new motor . . .
RE: reglar vs hight test gas
RE: reglar vs hight test gas
In the 50's when an OEM called for premium, it meant something. We had a Buick that just could not operate on regular, I think at the time reg. was like 89 oct. My dad always used super prem. 100 oct. Chevron (white pump) fuel. I think the cost was something like $.39/gal. !!!
On this same question, I had a 77 Kawasaki that I rode to Mexico City and back in Jan. 1980. You can only get bad and worse grades of Pemex down there, Extra and Nova (Spanish No Va means won't go). After a couple days, you just learn to deal with the knocking...you can't miss the knocking on a bike. We were down there several weeks and, ultimately, had no problems except when we came back to the U.S.---Kept looking for a gas station...couldn't find one...Until someone recognized the fact that here all gas stations are not Green/White Pemex! Dumb, dumb, dumb.
Rod
RE: reglar vs hight test gas
It comes down to how much extra MPG you really get vs the difference in cost. It will normally be a close call, slightly favouring the lower grade fuel. Those selling the fuel tend to do the cost benefit sums when setting prices, and expect an extra premium for the extra power as well as the premium for the MPG gains.
There will be no MPG gains in low compression engines or in use with no high load component.
Regards
eng-tips, by professional engineers for professional engineers
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RE: reglar vs hight test gas
RE: reglar vs hight test gas
Should have some relevant info. The curve of bsfc vs ignition timing is presumably well known, as is the curve of ignition timing vs octane, for typical engines.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: reglar vs hight test gas
Pat, wouldn't you think that if one is shooting for max fuel mileage, there should be no high load component ?
Isaac, I think you methodology has as much merit as any. I'm a novice when it comes to fuel mileage. I read a lot and listen a lot, but I have never found the need to go crazy over fuel mileage. For me, a paid off gas guzzler is ultimately much cheaper (often more fun, too) than investing >$30,000 in a new car that will 'save' me ~$30/month!
Rod
RE: reglar vs hight test gas
It took me a bit to realize that was directed at me. I wasn't guessing about your methodology (or accusing you of anything). You didn't tell us anything about your methodology, and it was presented more in the nature of anecdotal evidence rather than scientific evidence. For all we know, you got the regular gas at the top of a mountain or on days you were hauling your boat with your mini Cooper. :P Or maybe your number was based on two mixed tanks of gas, for example.
I find the 20% number very surprising, practically unbelievable. I just wanted to know if such a number has been verified anywhere, or if upon reflection you thought your number was controlled enough to be presented as scientific.
RE: reglar vs hight test gas
RE: reglar vs hight test gas
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: reglar vs hight test gas
Ethanol is usually in at not more than 10%, and has 67% (roughly) the energy content, so that only explains 3.3% even if true, although anymore you can often find ethanol in any grade. 3.3% is significant, of course.
Now I'm curious - do you know the compression ratio of the mini? I assume it was not supercharged...
RE: reglar vs hight test gas
Different octane rating, then it gets more complex due to many of the factors already covered as well as the different a:f and energy content.
I have a very unscientific test. Every time I refill, I reset the trip meter. I watch the mileage vs gauge. It is a pretty good indicator of whether I am doing better or worse than normal.
Occasionally I try private brand or independent fuel, sometimes ethanol blends, sometimes higher octane, but I guess about 95% of the time I use std unleaded which here I think is typically 89 to 91 depending on brand.
Regards
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RE: reglar vs hight test gas
1.6L 115 hp I4
10.6:1 compression ratio
RE: reglar vs hight test gas
For the best (lowest) BSFC, you want the engine operating very near its maximum load, and typically at its peak torque. For any lower throttle setting, the engine will perform less efficiently (power produced by the engine is lowered, but all of the rotating friction losses are still there - think of an engine at idle speed, barely producing enough power to keep rotating, but still burning fuel: its efficiency is pretty much zero).
Unfortunately, most of us like to drive cars that can accelerate hard enough to be at freeway speed at the end of an on-ramp, thus the peak power we want is quite a bit more than is required for "cruise". Thus, we have systems that shut down part of an engine (one side of a v-8) or reduce pumping losses (Toyota VVT), or hybrid systems that use stored electrical power to provide acceleration, while the IC engine is sized for the cruise condition.
RE: reglar vs hight test gas
IMO the older engines had to spin up to become efficient, but my Z06 runs 1500 RPM at ~65 with 24MPG.
I run the 87 octane and have had no problems but I have not done a mileage check other that the computer trip mileage.
I don't know anything but the people that do.
RE: reglar vs hight test gas
As for price, I love it. The gap between low and high octane is a constant $.20/gallon. As gas has gone up, the % in price has declined.
RE: reglar vs hight test gas
Here's more anecdotal data- I have a Volvo V70 2.4T that 'recommends' high test (91 RON, if memory serves) but 'allows' regular. I understand that advanced timing theoretically should give marginally quicker accel and maybe even smoother run, so I wanted to justify fancy gas. On several trips to grandma's house I alternated fill-ups with 87 and 93 AKI and recorded mileage. The difference compared to standard deviation convinced me that I couldn't tell a mileage credit for fancy gas. Maybe now that premium is relatively cheaper I should try the experiment again using in-town service.
Is there a CAFE requirement that OEMs have to recommend the same fuel grade they qualify models with?? I'm still wondering what's in it for them to call out fancy gas unless they believe it reduces their warranty costs or customer complaints- but I doubt many average drivers would complain that their mileage or acceleration was noticeably different.
RE: reglar vs hight test gas
That said, I tend to go with performance. In winter, the low-test fuel performed better. In older cars with knocking or dieseling tendencies, premium fuel in the hot summer helped avoid those difficulties.
RE: reglar vs hight test gas
Just bought fuel and for the first time in ages the spread was more than 10 cents. only 11 an 22 but still ...
I'm pretty sure there are vehicles that are more economical to operate on premium ( I hope so, I've put considerable effort into making it so.)
That said, I'm sure there are a thousand times as many wasting money on unnecessary octane
RE: reglar vs hight test gas
Ok, you probably have me there, my numbers are from memory for 4-cylinders...
But my point is (was) that running an engine at a higher load gives best efficiency. Compare your numbers to my 4-cylinder 1.8L that runs ~2500 rpm at 65mph with 33-34 mpg. I would bet it puts out something a bit closer to its maximum load (as a percentage of its capability) at that speed, relative to a V8, thus it gives better mileage. Your motor would pretty much tear the shorts off mine in a drag race, but the little motor wins in efficiency, simply because it better matches the average driving power requirement.
RE: reglar vs hight test gas
I had a turbo T bird that I spent money on that my wife got 33 MPG and I got 16 MPG so driving a 4 Cly isn't the complete answer to good mileage. A side note; in 4 years I went through 3 turbos and 2 motors...also expensive..
I don't know anything but the people that do.
RE: reglar vs hight test gas
One...If your wife averaged 33mpg, she probably needs a new calculator or, a Hondayota something or other.
Two...Since you got 16mpg, I certainly can see why you went through three turbos and two engines. I approve but, you shoulda had me do your new engine.
My wife and I averaged 22/26 mpg from new until 100k miles where she holed a piston...crapping the turbo, etc.
New engine (Evelrod Racing build @ 295hp at the rear wheels on the JBA dyno)...we managed 22mpg most of the time and that engine went over 200,000 miles! Sold it because we could not keep an AC compressor in it and it wouldn't pass smog last time. I liked that car!... "1983-1995 RIP" Sure was a fast car. Used it in many, many SCCA schools at RIR and Willow Springs...fast on the dry lakes too, 155mph on the rev limiter...clocked!
Rod
RE: reglar vs hight test gas
I agree with Rod's mileage observations, but IMO a stock 2.3T has plenty of safety margin when maintained in tip-top condition, and as he notes, when judiciously modded, is capable of vastly increased power without sacrificing longevity.
RE: reglar vs hight test gas
I suppose I could have backed boost down to some 'reasonable' numbers...what fun would that have been.
I could spin the tires going into second gear (first was kinda doggy...low boost) and it would go plumb sideways into third. Coming out of T-9 at Willow, I could 'haze' the rear tires in 4th gear!!! I know. I'm too old for that...NOT.
Rod
RE: reglar vs hight test gas
The next one just sucked in the impeller and contaminated everything.
And the last one; I was told to let the turbo idle down as there was no reserve oil to the bearing and should have listened, if I do it over again I would PAY attention its cheaper that way.
Cheers
I don't know anything but the people that do.
RE: reglar vs hight test gas
RE: reglar vs hight test gas
I doubt if I will ever buy another street driven car with a turbo unless there is some very large profit in it for me.
Rod
RE: reglar vs hight test gas
In my case my DD has been the Ford 2.3T '85 vintage for the past 16 years and have never had a turbo failure. I've torn down & reassembled the turbo a few times, but only the first time was for maintenance (compressor seal passing oil), the rest were mods in pursuit of higher performance, so I'm just now on the third set of bearings/seals at 200,000 miles. Just to fill in the picture, I'm currently running 22psig boost (at 5000' elevation), and expect to have around 300 whp when tuning is complete.
Sorry for the thread hijack; we should start a new thread I guess if this turbo discussion has legs.
RE: reglar vs hight test gas
I have only lost one turbo due to ignorance, I guess. That was on my Corvair Spider in 1964. The first turbo in the Bird was cratered due to the molten Al from the piston failure at 100k miles. The turbo on my Dodge/Cummins, now at >200k miles and 17 years old, is doing just fine.
Rod
RE: reglar vs hight test gas
Cheers!
RE: reglar vs hight test gas
RE: reglar vs hight test gas