Gas

I usually put 89 Octane in my 03 S-type. I have also tried 91 and 87 Octane. Performance is same on all. No knocking. So why buy expensive gas? 

I believe it is more of a long term benefit to use the recommended octane levels. Keeping the fuel system clean is important for keeping performance and fuel economy at their best.  I am afraid if I use poor quality gas, I will be forced to do a fuel injection service, replace the fuel filter, possible throttle body...just doesn't seem worth it to me. It's gucci gas for me I am afraid.   You can always be our guinea pig...lol?

Cali boy
Something to think about.
If you buy gas at 3.00 and you get 20.00 worth, You get 6.666 gals.
If you buy gas at 3.10 and you get 20.00 worth, You get 6.451 gals.
As you can see your only getting .215 gals less by buying the higher price gas. The saving is only .645 cents between the two. Buy the higher Octane and take care of your car. Is 64 cents worth the price.
Guess you never thought of it this way.
Regards

.

We see many cars coming in that use cheap gas. Injector problems, pinging, knocking, poor econmy etc.
You only pay a couple of bucks on a fill up extra. Money well spent.

I tried the lower octane once I noticed a difference in performance. Since then I have stuck with the higher octane. As oilman points out it is not a huge difference in the final price. Its just harder to choke down the nearly 4.00 a gal in Dallas!

Dear god I tried the cheap stuff a few weeks ago and couldn't wait to get rid of that crap. My car went from 300hp to no more the 200. Never again, my car is so use to Shell's V-power that if I put anything else in there the car suffers.

  I was wondering...I filled up my S-Type almost 2 months ago(I used only a quarter of a tank)I didn't drive the car and now the check engine light is on. Could it be the gas?

could be anything.. gas is possible.. may just be a simple misfire..

I'm sorry, but if your car runs fine on lower octane, run the lower octane. Their are sooo many wives tales that go along with octane ratings so here is something to remeber:
1. If you run lower octane, and do not get pre-ignition, you will not gain ANY power by going with a higher octane.
2. Higher octane is NOT "cleaner". In fact, EPA regulates how clean gas has to be. And when you see advertised gasolines as being SOO much cleaner, you are usually paying for your gasoline to have water added to it.
 
It is quite interesting when people want to purchase higher octane fuel. If they knew the chemistry behind it, they would actually buy lower octane. Why is this? Because, simply put, the higher the octane rating, the slower the gas burns. In a simplified chemistry version, gas has basically octane and heptane. The number you see at the pump is the average percentage of octane. Funny thing is, octane burns slower.
 
 

^^^^ Burns slower....? Hmmm, so are you saying that 93 would last longer than 87?

I have to agree with rianbech if your motor does not knock with 87 why put in 93. It is all advertisement. Just like BMW wants you to spend $9.50 a quart for thier special oil when mobil one or
castrol will protect just as well. Profit is the name of the game.

quote:

ORIGINAL: Igloo112

^^^^ Burns slower....? Hmmm, so are you saying that 93 would last longer than 87?

 
In fact it does last longer. In the combustion chamber that is! It will still inject the same amount so a tank of gas won't last longer.

i only use 93 in my car, where i bought the car in Texas and coming back they had 91, and 92 octane as the highest levels avail at some stations. Even with that I noticed a performance and fuel economy diff. in favor of the 93 octane. My car has never had gas that contains ethenol in it either. Lately, ive had to turn around and leave many stations I normally go to but I refuse to put it in any of my cars.

I come from turbo cars where octane is so debated and capitalized upon. I personally like is a mild to cold climate (west coast) and use 89 in the winter. In the summer/spring/fall I use 92.
 
I use Chevron exclusively.
 
Remember Chevron higher octane gas is still the same gas at lower octane gas but with additives that make it burn slower. Very little difference in quality.
 
Bob's corner gas bar? Who knows where he buys his gas from. Chevron ONLY put Chevron in their tanks (in Canada at least) and you know what you are buying.
 
this is debated ad infinitum on line especially amongst motorcyclists and turbo owners. buy what you want. Spending money on expensive gas over the lifetime of a car or buying synthetic oil equates to a full engine replacement for some cars (price point varies).
 
Drive your car better (and maintain it) and cheap gas is the smallest variable. Filling your tank after the drive and parking it full in colder temps is THE BEST insurance against any fuel issue. Less chance for condensation on the tank.

Added ethanol will cause a loss of mileage and marginal loss of performance. HOWEVER, living in California I have had to deal with added ethanol (every station has to add it here). After 2 engine builds, I support it. The first 350 I built ran it's entire- 85,000 mile- life on ethanol added gas before I replaced it with my current motor(nothing wrong with it when removed). I tore it down for a rebuild to sell it and was amazed by the condition. The valves, exhaust ports, quench area, and combustion chambers looked brand new! Plus ethanol is even more slower burning than gas, raising the effective octane rating. This lets you raise the compression ration and run on pump gas. My new motor has a static compression ratio of 12.2:1  I wanted to run it on pump gas from the beginning of the build and thought I'd have to go with a custom cam to lower the DCR. However, with the added ethanol fuel, i dynoed and broke the motor in with no problems.

    This debate always drives me nuts. Why would you use a lower rated octane gas for an engine not designed for it. Just because you can''t physically hear engine knock doesn''t mean detonation still isn''t occurring. You can''t tell unless you hook a monitor up to your car and check for it. All your timing tables are designed for higher octane gas. Yes, your knock sensors will compensate to some extent for crappy gas, but why make them. Also, higher octane gas goes not give your car more horse power. More octane makes the gas less combustible and and resistant to detonation allowing you run run a more aggressive timing table (which does allow for more horsepower if properly tuned). All-in-all, the higher octane gas make your engine run better.

For engines designed for lower octane gas then you''re right...the higher octane is generally unnecessary and a waste of money. For engines like ours, you''re just wrong. Spend the extra $5 per fill, take it easy on your engine and use what it''s designed for...

Remember, if you can actually hear the knock then it''s pretty bad...