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Fuel grades?

5K views 39 replies 27 participants last post by  pkmcd99 
#1 ·
Anyone notice major differences in the fuel grades or is it just as good using 87 oct with additive?
 
#3 ·
I have run 89 octane for all but two fill ups. Those two were 87. Engine was noticeably louder with 87. To me the extra $1.25 a tank is worth it. MPG is a hair better but probably less than 1 mpg gain.
 
#4 ·
The Ugly Jeep said:
I have run 89 octane for all but two fill ups. Those two were 87. Engine was noticeably louder with 87. To me the extra $1.25 a tank is worth it. MPG is a hair better but probably less than 1 mpg gain. I have just over 12000 miles and it's a3.8
 
#6 ·
There is zero advantage to running a higher octane than recommended by the manufacturer in any modern fuel-injected engine. If the engine is designed and programmed for 87 then 89 or 92/93 will have no effect other than to cause you to spend more money.

Any positive effects you notice are placebo effect.

However, if you've modified your engine programming (through chipping or a programmer) to advance timing then you should use the octane rating recommended by the chip or programmer.

Now there are differences in the fuel additives from different distributors though the additives are the same for all grades from a given manufacturer. So there may be an advantage in buy a brand name fuel (Shell/Marathon/Exxon) over what you get from your local Super Sloppy Mart.

FYI: http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm

 
#8 ·
love the sign

:dance:Love the fuel sign:punk:
There is zero advantage to running a higher octane than recommended by the manufacturer in any modern fuel-injected engine. If the engine is designed and programmed for 87 then 89 or 92/93 will have no effect other than to cause you to spend more money.

Any positive effects you notice are placebo effect.

However, if you've modified your engine programming (through chipping or a programmer) to advance timing then you should use the octane rating recommended by the chip or programmer.

Now there are differences in the fuel additives from different distributors though the additives are the same for all grades from a given manufacturer. So there may be an advantage in buy a brand name fuel (Shell/Marathon/Exxon) over what you get from your local Super Sloppy Mart.

FYI: The Low-Down on High Octane Gasoline

 
#7 ·
Octane rating is the measure of a fuel's resistance to pre-detonation. Higher compression engines need higher octane (more resistance to pre-detonation) to avoid the spontaneous, early detonation of the fuel mixture on the compression stroke, which is noticeable as engine knock or pinging. Higher octane fuel does not have more explosive energy than lower octane so unless you've upped your compression ratio or advanced your ignition timing, which is what the Superchips do for you, there is no advantage to running higher octane.

On high compression engines, the higher octane fuels don't make the power. They just keep you from blowing head gaskets due to uncontrolled explosions of the fuel.
 
#10 ·
Ethanol is actually used to raise the octane rating for gasoline. Pure ethanol has an octane rating of 113. But as you noted has less energy than gasoline. So it's possible to get worse mileage with higher octane fuel if the distributer is using ethanol as the sole octane booster.

On the other hand, ethanol absorbs water and as it does (in high humidity) it actually lowers the octane rating of the fuel it is mixed with so your higher octane pump gas may lose as much as 4% of it's octane rating as it ages in your tank.

But given that the EPA has banned all the good octane boosting chemicals and the guberment subsidizes the ethanol industry we have the byproduct of our elected officials.

All for our own good since they know best. :whistling:
 
#15 ·
Mr. Sinister said:
My 2010 pings under load on 87 and 89, so I run 93. No ping.
Average mileage is 18mpg back and forth to work, 24-25 pure highway driving, calculated by hand.
Bone stock auto drivetrain, wheels, and tires. Just a spacer lift.

Just the facts.
We discussed this before. After installing the 35's and setting my tune to stock, the jeep would ping pretty good accelerating. Especially @ lower Rpms.
Doesn't do it tuned if I'm easy on the gas.
Also if I don't use Shell gas. If I'm near empty and fill up somewhere else I hear some light knock/ping under load.
With Shell gas she's quiet..... Strange :)
 
#18 ·
Running 89 octane wouldn't be too bad. There probably is a slight difference but doubt the cost will out way it but I guess it could very slightly. Other then that, without a tuner higher octanes are not tuned for your Jeep. Tuners like Superchips can tune the engine for higher octane but without a tuner it just isn't worth it.
 
#24 ·
I'm still on my first tank but that tank is 92 octane non-ethanol.

So far, the computer is telling me that I'm averaging 14.2 mpg.

Do I care? Not really, but I'm going to do it for a couple more tanks as an experiment.

Then I'll probably switch to 87 and never look back.
 
#25 ·
I believe the 3.8l has knock control. No modern engine with it should ping regardless of load. If it is, it is a sign something else it not right (tune, plugs, knock s sensor, O2 sensor...)

OP, higher octane does not mean "better". If your engine does not need it, you are wasting your money. You will get no better performance either as you engine cannot benefit (unless you adjusted timing via chip or slapped on a supercharger)
 
#27 ·
normally I would agree, but I have heard the difference on my 2010 first hand :) It doesn't sound like pre ignition knock though, it actually sounds like valve chatter, which also shouldn't be affected by octane at all, but running higher octane quiets it nonetheless. An oil change will also quiet it down for a few hundred miles.

I haven't tried different gas stations though... might have to shop around and see who has better gas.
 
#29 ·
When I had my 350Z, one of the guys on the monthly group drives we did in the summer time told me Shell was supposed to be the best. Apparently he and his brother who both had 370's send their oil off to some lab every time they change it and it always gets changed with some kind of "special" oil and one of the tips that they got from their lab guy is that Shell is the best to use. Obviously I can't really say how accurate that is, but I DO get better mpg off of it and the butt dyno likes it as well, but of course the butt dyno is subjective.

Octane ratings, always go with the mfr. recommended unless you're running some kind of special tuning, turbos, supercharged, etc. If you really are having problems on 87 in a non-modified Jeep, something is wrong. Either bad gas, or a mechanical issue.
 
#32 ·
There is about a 5-7 cent a gallon difference in NC for E10 gas. When you say 25 cent difference is that E10, E15? I don't think our engines are rated for use of more than 10% ethanol blends/

Ethanol has 34% less energy than gasoline. So any ethanol blend will result in worse fuel economy in proportion to the amount of ethanol in the fuel. In the case of E10 that would be up to 3.4% worse mileage. Whether or not that works out economically in your favor depends upon the savings over lost mileage.

In NC when fuel is $3.85 (without ethanol) vs $3.80 (E10) then I'm only saving 1.2% while getting 3.4% worse mileage so economically it makes sense to avoid E10.

There are other potential long term drawbacks to using ethanol in your vehicle but Jeepers aren't the most gentle users of vehicles so YMMV.

I vote no to ethanol and avoid fuel stations that indicate its use.
 
#39 ·
Premium vs regular gas was on the pro side for the Wrangler in the pro vs con for my existing FJ or prospective new Wrangler. The FJ from 2007 to 2009 required premium. When Toyota tweaked the 1GR-FE in 2010 it changed, but up until then the FJ required premium. The manual FJ being full time 4WD had a MPG of 16.5. That was in San Antonio, after I changed the plugs. Because of the gearing, the 75+ mph that is common freeway speeds in metro Detroit was a killer on MPG; of course where speeds are MUCH slower in San Antonio it wasn't an issue. It is not uncommon to find drivers in the passing lane on the interstate in San Antonio driving 15 mph under the posted 60 or 65. Driving that slow in Detroit will get you shot. With the FJ in 6th gear, 2000 rpm will get you 60 mph. That 2000 rpm is on an engine that redlines at ~5500 and peak torque at 3600. In the Wrangler in 6th gear, 2000 rpm will get you near 75 mph, and that is on an engine whose redline and peak torque is about 1000 rpm higher than the Toyota. So my MPG is enormously better with the Wrangler AND on regular not premium. Fella, be happy you don't have to put premium in that filly and ride her until the sun sets. Yeee ha.
 
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