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Premium vs regular gas

i am looking to buy a used Acura '04-'06 but am concerned that only premium gas is recommended for these engines.does this mean i can not fill up with regular gas and if i do,what could go wrong?

What could mostly go wrong is valve wear or damage. If you buy such a car and use an 87 octane gasoline, you will notice a clacking sound sometimes, especially while travelling up a steep hill. This is not going to kill the engine overnight but it’s not good.

You will have less power accelerating. You would get around the same gas mileage, although the 87 octane might actually be a little better.

So you are going to buy a car and I would guess two of the reasons for choosing the car is good fuel economy and power.  

If you use regular you will get lower fuel economy and less power and maybe damage to the engine.  I would suggest that if you don't want to use the fuel specified by the maker, then you should look for a different car.

This is asked here over and over and over. The existing threads will answer your question. Please search for them.

In a nutshell, your car will change it’s engine performance parameters to compensate for the lower quality fuel, resulting in lower efficiency, less power, and fewer miles per gallon.

The price difference between regular and premium is about 20 cents per gallon.

Lets say you drive 1200 miles per month, and get 20 mpg. You’ll use 60 gallons of fuel, a price difference of $12/month between premium and regular. Wow.

But with the regular gas you’ll lose efficiency and mileage. Let’s say you only lose 1 mpg. Now you’re using 63 gallons per month. So you’re buying 3 more gallons of fuel. At today’s prices that’s about $12. You’ll save NOTHING.

This question is probably the most-often asked question in this forum. Using the search engine at the top of the page will probably locate a few hundred similar questions with appropriate answers.

To summarize:

If the auto maker states that premium gas is required, use of regular-grade gas will result in engine damage over the long-term, especially if the knock sensor is no longer functioning.
You will definitely get less power from the engine, thus making this Acura less of a performance machine than it was designed to be.
You will get fewer miles per gallon when using regular-grade gas, simply because the engine will self-adjust its timing in an attempt to avoid damaging engine knock or “ping”. When the timing is retarded in this fashion, the result is reduced fuel economy, as well as reduced power.
Your engine may develop damaging carbon deposits.

So–as was said or implied, decide whether you want an Acura or whether you want a car that can safely be operated on regular gas. If you want an Acura, you must use premium. If you want to be able to use regular-grade gas, you should not get an Acura.

If you buy a Honda, it will cost less and use regular gas.

Don’t buy a premium vehicle if you can’t afford it’s operating costs. There are millions of vehicles out there to choose from that operate on regular gas just fine.

If you don’t want to buy premium gas, or can’t afford premium over regular, don’t buy this car. It is made for premium fuel and using regular can damage valves, and pistons. Both very expensive repairs. Meaning the money you save on regular will put your car at risk for a multi thousand dollar repair. Pennywise and pound foolish.

Here’s a link to Tom & Rays article on this.

You can’t afford the extra $4 to fill the tank?

Maybe you should consider another regular gas burning vehicle instead.

As to what can go wrong that all depends. Maybe nothing will happen or the engine could be destroyed. There are different factors involved and even 2 identical cars may have different characteristics. Some handle regular better than others and proper EGR system operation is critical also.

It’s recommended that my Lincoln use 91 octane but both my prior Lincoln and current one run just fine on 87 octane and even on 86 and 85 octane when in the mountains of CO.
No loss of power, no drop in fuel mileage, etc. Matter of fact, the fuel mileage while using 85 octane in the mountains actually goes up about 1 to 1.5 MPG.
Reading the spark plugs shows there are zero problems and after a couple or three hundred thousand miles of this practice I have yet to see a downside.

Five octane points just isn’t enough for either you or you engine to notice it very much…Spark knock today is almost unheard of, regardless of what grade of fuel you use…

Your Lincoln engine is designed for an entirely different set of operating conditions than his little Acura engine. Your Lincoln, I’m guessing, is sporting a V-8 engine designed for low rpm cruising around, and has two extra cylinders compared to his smaller 3.2 liter V-6.

His engine most likely runs considerably hotter, and has a higher compression ratio, which is most likely considerably closer to the limits of detonation if driven spirited, in comparison to your Lincoln engine.

This is especially true if you’re driving a Lincoln Town Car, with the same engine used in Ford Crown Victoria’s, which only needs regular gas to get around town with. His 3.2 V-6 wasn’t used in anything at all in the Honda lineup during that time frame. So it was designed for the Acura lineup, and designed to be used with premium fuel in order to get all 270 hp out of it.

I bet the TL engine is considerably more expensive to replace than the motor in your Lincoln, too. Are you going to offer part of the money to him to replace his engine if he takes your advise, and his engine dies?


The compression ration on my Lincoln is around 10/1 and the Acura is around 11/1.
My point is not that the OP should not use Premium at all; it’s that this should never be a one size fits all issue.

It could be that a 2004 Acura TL MUST use Premium or ruin an engine. To ruin an engine would mean that someone is continuing to hammer the throttle in spite of a ton of rattling under the hood. This can also occur due to an EGR system fault.
Whether an '04 TL would rattle on regular with an operative EGR I have no idea but if it did then I would certainly say that Premium is necessary beyond any doubt rather than turning up the radio to drown it out.

My Lincoln is a Mark VIII and it uses a 4.6 but it’s not the same engine as used in Crown Vics. It’s similar to the one in the Mustang Cobras with 4 overhead camshafts and I assure you it’s a pretty high-tech, and expensive, affair. The owners manual states 91 octane is to be used in this engine but after 10 years of use and countless miles there has been zero problems.

As to temperature it runs at around 195 which is what I assume the thermostat on the TL allows it to run at.
As to revs, the 4.6 is actually at its best when being revved. It’s a high winding motor.

Bottom line is that I would never tell anyone to go out and thrash their engine by ignoring warning signs like rattling. I’m only pointing out that one size does not fit all and that regular may, or may not, be used with no problem. If there IS rattling then I would be the first to say fix the EGR system or use premium.