Premium gas


I am reading conflicting reports about whether it is necessary to use premium gas in my 2002 Lexus 430. What is your opinion?


What does your owner’s manual say?


I believe the owner’s manual for this vehicle specifies premium fuel. I suggest you use ONLY what the owner’s manual says.

The high-performance engine in this vehicle needs the octane in premium gas to perform properly and avoid premature ignition, which can damage the engine.


Think of it this way. You paid good money to buy a high end car because it has high marks for performance and luxury. If it didn’t, you would never pay the prices that are charged for these cars.

Now, after paying all that money, why in the world would you go and short change yourself in the name of saving two measely dimes on a gallon of gasoline???

High performance engines use premium fuel because they require higher compression to create more power. Higher compression will detonate lesser grades of gas. Some high performance engines can adapt to run with lower grade fuel, but at the loss of TREMENDOUS amounts of horsepower. Using 87 in an engine that is designed for 93 can cost you more than HALF the engine’s horsepower output. Your fuel economy will suffer just as terribly. In this situation, I think it’s a no brainer as to which kind of fuel you should use. =)

As for engines that REQUIRE premium grade fuel, these engines are the same as the previous kind of high performance engine, except that they can not adapt to lower octane levels adequately. Fill your tank with 87, and listen as your engine detonates itself to self-destruction. In THIS case, I think the answer is even more a no-brainer.

I figured I’d include all of this information instead of a more simple answer, so that you could understand exactly WHY you need to use premium fuel in an engine that demands premium fuel. However, I will also echo the simpler explanation of my forum-mates: Respect The Owner’s Manual!!! Always and forever. If the owner’s manual says jump, turn to the next page to determine how high.



You definitely need to look in your owner’s manual. While I’d be the first to testify to McP’s expertise, the LS engine may not be a high compression engine.


When you read the fuel requirements in your owner’s manual as was said repeatedly before, the key words are “recommended” or “required” or something similar such as “should” or “for best performance” or “must” or “to prevent engine damage”.

Note under the Second Opinion section near the end, a 2002 Lexus owner inadvertently used regular and complained without being specific about it that his engine ran terribly. My guess is that it lost a little full throttle power.

Try a half tank of 87 octane to see how it does if your owner’s manual permits 87 octane. If it makes a problem, then fill to the top with premium.


If the manual states requires you should use it.

However its a free country and YOU pay future repair bills so you can do as you please.


I don’t know what the compression ratio is. I called it a “high-performance” engine, which, in my opinion, it is.


I understand. My point is that I’m not sure the LS has a high performance engine. It being the luxury land sled without any boost from a T-charger or supercharger, it may have a compression ratio designed to accept regular without pinging.

The owner’s manual is the definitive authority anyway.


The only opinion that counts comes from your owner’s manual. If it says premium required, that’s what you should use. At best, the car will run badly on a lower octane fuel and it may very well suffer damage. If premium is merely recommended, you can get by on less, but the car probably will not perform as well. This would include poorer gas mileage which would offset any savings.