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Regular gas versus high test

I have an 2008 Acura TL Type S. The owner’s manual and the tag on the gas tank door insist that the car must have high test. Others are telling me that’s completely bogus. Will it hurt my TL in any way to start putting regular gas in it?

I doubt it will hurt you…but the reason you are asked for high test is due to the compression ratio of your pistons. For TOP performance you need high test. The reason behind this is that high test fuel is LESS suseptible to pre-detonation (or pinging) Ever hear an older car going up a hil and it was knocking and pinging? You Mfg doesnt want this to happen as it is VERY harmful. With the computer controls on your Acura your engine will hear any pinging far before you and simply run the engine at a lower power until the pinging goes away

Low octane fuel is MORE suseptible to pre-detonation…so you will notice less performance with low octane…but the car will not let the low octane hurt it or at least it will try not to…it will simply back off in timing advance to protect itself.

With high compression the cylinder temperatures are higher when it is in the compression stroke…due to MORE compression… WHen you use a low octane fuel…that fuel is more prone to igniting early…before the piston reaches the top of its stroke…if that happens then it ignites early and the explosion smashes down on the top of the piston and in the valves faces. This is harmful…and is the Pinging sound you heard in those old cars…No amount of timing adjustment can prevent this from happening when it is hot outside…so even though your car will try to adjust for this…high cylinder temps and high compression pistons can ignite low quality fuel early…which is BAD… This is what happens in a Diesel engine…although at the right times…

SO…I think you could get away with using low octane…but it is at your own risk I guess…I doubt you will have problems, but god forbid if you ever hear pinging…Immediately switch back to the normal recommended octane to keep your pistons happy. I think you can use it but I listed for you what is happening and the reasoning behind it. I know people who disregard the octane advice…but the issue is very real… You decide…but if you use it…listen to your engine…if you hear pinging…then forget it and use the better fuel.

You should be using premium in this car. The sticker is there for a reason.

Check owner’s manual for “must” or “recommended”.

Best Case Scenario:

The car will experience knocking and the knock sensor will detect it and thus retard the timing. This will result in lower gas mileage and less performance.

WORSE Case Scenario:
The knock sensor will fail and won’t retard the timing when knocking is present. This could result in severe engine damage requiring a new engine or rebuild.

Your choice:

If your Acura is designed to run on anything less than premium fuel, the owner’s manual will indicate that.

Of course you could disagree with the manual and take the advice of people who had nothing to do with creating the Acura’s engine and might want you to believe there is a conspiracy to get you to pay more money for an unnecessary quality of fuel.

Are you feeling lucky?

Your engine was engineered for optimum performance with premium fuel. The engine control computer is sophisticated enough to prevent any major engine damage that may be caused by lower octane fuel. You won’t really hurt the engine with regular, but you will lose efficiency, and thereby miles per gallon. So you don’t gain anything either.

Here’s the math:

1200 miles/month at 25mpg = 48 gallons used.
48 gal of premium at $3.699/gallon = $177.55
48 gal of regular at $3.499/gallon = $167.95
You’ll save $10/month. Whoo hoo!

That’s assuming no loss of fuel economy though. Let’s say for argument’s sake you’ll only lose 1 mpg. Now:

1200 miles/month at 24mpg = 50 gallons used.
50 gallons or regular at $3.499/gallon = $174.95
You’ll save $2.60 per month.

$2.60 a month. Heck, even $10 a month. Is that really something to consider with a $35,000 car?

If your owner’s manual says “premium required”, you must use premium or potentially face serious engine damage. If it says “premium recommended”, you can skip the high test, but will lose some performance and fuel economy by doing so. Either way, I would use the fuel recommended for the car and nothing less, especially with such an expensive car. Saving a couple dollars every fill-up isn’t worth the risk and loss of some of that driving experience offered by a sporty, $35,000 car. If you can afford such a nice car, a couple dollars extra every fill-up for the proper fuel shouldn’t be an issue. The price difference is only $.20 a gallon, or just $2 per 10 gallons. Less than many people pay for their morning latte.

It looks like we are all in agreement. If it asks for it then it does so because of the reasons that I and others have stated. It doesnt give you any advantage to use the low octane there are only downsides to using it…Can you “get away with it” probably…SHOULD YOU? Prob not… All of us on here know why the Acura asks for that type of fuel…ASEMASTER certainly stated it clearly enough. I am in agreement with him that your engine computer will TRY to compensate for this lower grade fuel…but it can only adjust itself so far…and while adjusted it is not running to its peak performance level or its MPG potential. It also may not be able to adjust the timing far enough to prevent detonation which can and will take place in a hot engine under load…I dont see any reason for going with the low octane…While you may save at the pump…the way your engine will be running, the potential damage that could be done and the MPG you will suffer dont add up to any advantage… All of us are basically saying the same thing here…

You bought a premium car with premium performance, why do you want to skimp on the stuff it needs to run?
Sell it now and buy an Accord or Civic, THEY run on 87 octane

Will using regular over high test really save you any money?

Regular costs about 5.5% less per gallon than high test ($3.60 vs $3.40 per gallon.
Let’s say your car normally gets 20 miles/gallon.
If using regular gas causes the mileage to 1.1 mpg, then you just lost 5.5% of your mileage. This means you got all the engine risk, poor performance, and you didn’t save a cent.

If your mileage drops more than 1.1 mpg in the above scenario, then switching to regular just cost you more money than high test.

Funny that you didn’t rate MikeInNH’s answer. You need just the octane rating that keeps the car from making a sound while climbing a steep hill. I don’t call it a knock, it’s more of a clacking sound. If you do hear this kind of sound climbing a steep hill when you are using a lower than recommended octane, then pay for the higher octane gasoline.

I’d give it the 89 octane and see what happens. Put high test in if you hear any clacking noises ever.