I think the key thing is to stay consistent with whatever you choose. I remember when I first got my SC400 with 100,000 miles I accidently put in regular the first time I pumped. The car was used to taking premium all the time, and I noticed it idling kind of funny. So I assume as long as you stay consistent it shouldn't do much harm.

 

your performance might suffer as higher quality grades include more cleaning detergents and high-octane gas is formulated to burn slower than regular, making it less likely to ignite without benefit of spark.The majority of cars are designed to run on regular gas, and that's what the manuals tell the owners to use. Higher-performance cars often require midgrade or premium gas because their engines are designed for higher compression (higher compression = more power), and regular gas may cause knock. If your car needs high-octane gas, and the manual says premium only then do it.

 

I've used both premium and mid grade. I notice a slight fuel efficiency penalty with mid grade but it isn't terrible. Also, mid grade causes my engine to run just slightly rough compared to premium. But overall, I'm quite OK with both. Never used regular gas though.

On a different car (06 Acura RL), I've used mid grade all the time and it runs just fine - 42,000 miles and going strong.

 

I learned my lesson with an SC 400 I used to have. That car called for premium, too, but somebody told me it made no difference. When gas was so high, I decided to put non-premium gas in it. It didn't take long before the engine was cutting out and stalling. I went back to the premium gas, but by that time, the damage was done (so to speak).

Going back to premium made no difference and I thought I had ruined my engine. I took it into my mechanic and I'm not sure what he did, but he fixed the problem. He performed some kind of carbon blow out and it worked.

I've always heard that if it says "Premium Recommended" that you can use any gas you want, but if it specifically says "Premium Required" (like the SC 430 does), you need to stay with premium only.

 

in the past, i would have said if you can afford an sc430, you can afford premium gas. but with the way our value's have dropped in the past two years, i guess that's not necessarily true.

 

Whatever the highest octane and most expensive gas is at the pump

 

I have been using premium only and have not had any problems. For and extra 20 cents per gallon, it's not worth the risk!

 

As I was reading this thread, I was thinking the same thing. For an extra $3.00/tank, I can use the best fuel I can find.

 

It's not really the cost...I suppose it's my upbringing. My father was in the oil business and he always taught me to use the lowest octane that didn't ping. But that was in the days of carburetors, high compression heads and no computers. Today, the computers will retard the timing so that you could probably burn kerosene in it.

Si what I'm trying to find out is specifically what happens when you put mid-grade or regular in one.

 

Clean out the old gas with Chevron 91 Premium Gas and the Chevron w/ Techron additive.

 

I agree, if you're driving an SC430, you should be able to afford premium gas. The car will definitely perform better. SC owners spend more money at Starbucks than on gas !! The real issue is about 25 cents difference/gallon, doesn't your car deserve the BEST ?? IT'S A LEXUS !!

 

This is the best explanation I have found because octane is the ability of a fuel to resist detonation under compression:

Higher octane means the fuel is more stable, which is to say that it will resist pre-ignition. Pre-ignition being that the fuel in the chamber explodes due to heat before the cylinder head has reached top dead center. Some people think the fuel burns hotter, or creates a bigger explosion, or some crap like that, no, it's just resisting pre ignition. Why is pre-ignition bad? Well if you have the explosion occure before the piston is all the way up, that means your forcing a piston down, when it's moving up. Obviously for that fraction of a second that the explosion and piston are working against each other, your engine isn't making any power, and any power made after the piston starts moving back down is obviously less because some of the explosion has been wasted.

Modern cars do have knock sensors that help fix this problem, but it doesn't stop it entirely and knocking the engine due to pre-ignition can damage the pistons in the engine. Engines that have higher compression usually make more power because they pack more energy into the same space. This is why many people think that higher octance gives you more power, when in reality, higher octane only allows your engine to make 100% of the power it was designed to make. .

 

I've run mine on regular for over 20kmi so far and never a detonation or backfire or any other incorrect octane type problem. (I now have 60kmi on mine.) I get about 21 mpg. I talked to my service advisor at Park Place Lexus and he said that there isn't any reason that you can't run it on regular and many, if not most, do. If the engine acts up, then you go up a notch in octane, otherwise, don't worry about it.

This has been my experience in the past also. Unless your car is specifically designed to need premium, then you can usually get away with using regular without causing any problems. If it detonates, then using a higher octane fuel will typically take care of the issue unless you have carbon deposits. (If you have carbon deposits, there are various ways to get rid of those.)

I've also heard the same thing about the oil. No reason to use the expensive synthetic oil, it really isn't necessary. That one I found surprising. I'm still not sure that I feel comfortable putting regular oil in the SC430 over synthetic.

 

I think oil is a bit different. I genuinely believe that synthetic oil is superior to regular oil and will provide protection for a longer period after regular oil starts being burned up.

That said, I'm still stupid and change mine every 3,000 miles. I know, I know. But old habits die hard.

 

I know my mechanic would agree with you. He's been using Valvoline synthetic for a long time now, and Valvoline Durablend for older cars. The synthetic is more expensive, of course, but you also can go longer between changes. I go 5,000 between changes when I used the synthetic, and 3,000 with regular oil.