Any reason to buy higher octane gasoline?

motivez · 01-09-2007, 10:42 PM

The car I have is a V8 4.0L and the manufacturer recommends at least 89 octane, but suggests 93.

I really have no clue whether or not it's worth the extra price, what it does for the car performance, mpg, etc wise.. so hoping someone with more car knowledge can help me out here.

Regular is ~$2.15 here now, and the others are anywhere from 10 to 12 cents higher than the one directly beneath it octane wise.

What's the deal?

ArrestMeRedZ28 · 01-09-2007, 10:56 PM

I run 91-92 octane in my 1997 Z28.

The engine will retard the timing causing less power plus higher octane will net you a little bit better fuel economy for a little bit more in price so why not.

6SpeedTA95 · 01-09-2007, 10:56 PM

Most folks tell you NO, and the one's that do are ass hats and full of crap...

What year vehicle is it? What is the make and model?

6SpeedTA95 · 01-09-2007, 11:04 PM

If its a newer vehicle (pretty much EVERYTHING 1997 and up) then yes it will make a difference. You probably wont "hurt" the motor if you run the cheap stuff simply because the computers in 99.99% of cars 1997 on had pretty good knock sensors. So basically it listens for knock/pinging in the motor, when it hears it the timing of the spark/fuel is changed +/- so the pinging goes away.

If you put in the cheap stuff you'll see your gas mileage go down as well as the power the car is putting out because the computer will constantly be adjusting the timing under moderate load.

There is some minor risk to using the cheap stuff, it typically burns dirtier. The lower the octane the faster it burns, the higher the octane the more controlled the burn is. Slower burning fuel (higher octane) burns more completely in the combustion chamber resulting in a cleaner more even burn in the combustion chamber.

The other thing to keep in mind is that there is a slight chance depending on the vehicle that piston wrings could get warped as a result of uneven burning in the combustion chamber. This can cause some oil burning issues and in extreme circumstances blowby resulting in significant oil burning.

In summary, I'd run premium, it doesn't necessarily have to be 93 but at least 91.

7960 · 01-09-2007, 11:21 PM

run the minimum the manufacturer recommends.....anything more is a waste.

Scrum · 01-09-2007, 11:51 PM

Originally Posted by 6SpeedTA95

If its a newer vehicle (pretty much EVERYTHING 1997 and up) then yes it will make a difference. You probably wont "hurt" the motor if you run the cheap stuff simply because the computers in 99.99% of cars 1997 on had pretty good knock sensors. So basically it listens for knock/pinging in the motor, when it hears it the timing of the spark/fuel is changed +/- so the pinging goes away.

If you put in the cheap stuff you'll see your gas mileage go down as well as the power the car is putting out because the computer will constantly be adjusting the timing under moderate load.

There is some minor risk to using the cheap stuff, it typically burns dirtier. The lower the octane the faster it burns, the higher the octane the more controlled the burn is. Slower burning fuel (higher octane) burns more completely in the combustion chamber resulting in a cleaner more even burn in the combustion chamber.

The other thing to keep in mind is that there is a slight chance depending on the vehicle that piston wrings could get warped as a result of uneven burning in the combustion chamber. This can cause some oil burning issues and in extreme circumstances blowby resulting in significant oil burning.

In summary, I'd run premium, it doesn't necessarily have to be 93 but at least 91.

I know shit about cars.

Would running a higher/more expensive octane vs. lower/cheaper octane be more economical in regards to the info you posted?

7960 · 01-09-2007, 11:56 PM

Originally Posted by Scrumtralecent

I know shit about cars.

Would running a higher/more expensive octane vs. lower/cheaper octane be more economical in regards to the info you posted?

it's about a wash... you get slightly higher mileage (a few percent) but it costs slightly more (a few dimes) so in the end it works out to be about the same money/mile

BUT, if you factor in that higher octane may (*MAY*) burn cleaner or more completely than lower, if you run higher octane there's a SLIGHT chance you could avoid other problems caused by deposits

Diesel66 · 01-10-2007, 03:34 PM

run what they tell you to run.

More octane then the engine is designed for will decrease performance.

Dumpy Dooby · 01-10-2007, 03:53 PM

Howstuffworks "What does octane mean?"

ArrestMeRedZ28 · 01-10-2007, 04:09 PM

Originally Posted by Scrumtralecent

I know shit about cars.

Would running a higher/more expensive octane vs. lower/cheaper octane be more economical in regards to the info you posted?

it's pretty much the same IMO, the gas companies keep this in mind when pricing octane levels.

Like stated before, run what the manufacture suggests.

If your on a long trip and don't want to stop as much you'll get a couple more miles/tank on premium than on 87.

kinggovernor · 01-10-2007, 05:18 PM

this would be a great trolling thread on OT

Kytro · 01-10-2007, 06:38 PM

Lol I run mine on 98 octane. Dodgy old car with newish engine.

6SpeedTA95 · 01-10-2007, 09:43 PM

Originally Posted by Scrumtralecent

I know shit about cars.

Would running a higher/more expensive octane vs. lower/cheaper octane be more economical in regards to the info you posted?

Depends totally on the vehicle in question. If the vehicle has a knock sensore, most modern vehicles do, then after 500ish miles of driving you could see improvements in mileage and power, but its fairly vehicle dependant. I would recommend running what the MFG suggest. If you have any audible knock then definatley go up at LEAST one grade. If you have no audible knock you might try it for 1000 miles and track your mpg before and after and see how the math works, and see if the car performs better. It's not always worth it to step up, but in some cases even if its not recommended its worth it, a perfect example is the ford 4.6L V8.

6SpeedTA95 · 01-10-2007, 09:44 PM

Originally Posted by Diesel66

run what they tell you to run.

More octane then the engine is designed for will decrease performance.

Not really, thats a pretty rare circumstance.

Diesel66 · 01-12-2007, 05:11 PM

Originally Posted by 6SpeedTA95

Not really, thats a pretty rare circumstance.

more octane equals less likely to burn at the correct time. Modern cars can adjust to it, but it wont give you any better performance.