Wrong Gas!! Now What???

my friend offered to fill up my boat yesterday. i went inside to get something and when i came out, he was just topping off the tank with the cheap stuff, 87 octane. i always put premium in my tank. should i be worried? is there anything i can do about it now?

I don't think that you'll have a problem.

Most boat engines are tuned for 87 octane and running 89 or 92 is a waste on those motors.

In the off chance that your engine is actually tuned for 92 (premium) you might hear some pinging under extreme load.

Also, keep in mind unless your engine is set up for 92, there is less potential energy in 92 than 87 octane gas. That means less HP.

Depends on the engine. If it's the "regular" engine which "needs" 89 octane, you're probably fine. I wouldn't even worry about it. In fact, the only thing you'll probably notice is increased power, heh.

If it's the HO engine that requires 93, you might have more to worry about.

If it was only a few gallons, it wouldn't reduce the overal octane of the tank enough to hurt anything. If it's a lot, "it depends."

Your engine probably has a knock sensor that will cut timing, preventing any damage, but you might consider draining the tank into your car or something, or draining half of it and topping off with 93.

Another question is does your engine even NEED the 93 octane you've been using. If the manual says it needs 89, you're only wasting money and losing power by using 93.

Nothing.... Be excited that you got a full tank and not $10-20....

E.J.

If you find out it 'needs' 92 octane, just put a bottle of octane boost in the tank and don't let your 'friend' fill it up next time. Since you own the boat, he should pay for the gas though!

Greg

Micah,

I have to disagree with you a bit.

Octane is a measurement of a fuel's propensity to detonate. The higher the octane rating, the more energy required to ignite it. That means running a higher rated octane fuel than needed in an engine is a waste of money and energy (HP).

One benefit that you’ll see with higher octane than what is required is cooler running temps in the engine (old motorcycle trick on very hot rides to help keep the engine cooler). The lower temps are due to less heat (energy) being produced with each combustion cycle.

Unless your engine has higher compression ratio thus requiring high octane, it’s a waste of money to buy higher octane gas.

http://auto.howstuffworks.com/question90.htm

Disagree with what? I think you just said the same thing I did? heh

I said he might get more power with 87, and then said unless his engine requires it, he's losing power running 93.

Where's the disagreement?

Hold on, I need more coffee...

I re-read your post, I must agree!

well, i guess i will go check the manual. anyone offhand know what a '02 xstar manual says to use? thanks for the help

Hey Sean M, that house on the left in your profile is ridiculous, it has its own helicopter landing pad, a garaged boat lift, water on 3 sides, and stone lions on every side of it. I was out there wakeboarding one day and saw the owners cruise in on their helicopter and land right out front...

matt,

IF it turns out your engine requires premium, just go to the auto parts store and just buy a bottle of 104+ octane booster (or 2...depending on how much gas we're talking about) and put that in there. I did that once when someone put 87 octane in my old M3 (11:1 compression, no knock sensors) and it ran fine.

As is probably obvious now, the only effect of running fuel with an octane rating that is too low is detonation (bad) OR, if you're lucky enough to have a knock sensor, retarded timing and lower performance.

Matt - your engine should be EFI so no worries. All EFI engines are capable of burning whatever you can buy at the pump, the computer will adjust spark and fuel delivery to match conditions.

Older engines with a carb could not do this. You tuned it to what was in the tank and always filled with that.

Most newer applications will make more horsepower from higher octane gas. My wife has a Intrpid R/T with the 3.5 (poor man's 300M). The engine is rated at exactly 3 less hp than the same engine in the M. The difference is the R/T runs pump 87 and the M needs 92+.

You lost about 5-7hp for that tank, but no damage.

What's up, Matt. Just add some octane boost to that bad boy.

Lower pre-denotonates easier. Surely those motors have knock sensors and would retard the timing a bit. You should be safe. But mix with some 100 octan or just add boost and you should be cool.

Q: What should you do?

A: Thank your buddy and go boarding. As others have said your boat will retart the timing. Don't run it WOT if you are really concerned.

We filled up the boat with 93 octane by accident on the weekend instead of 87. I don't know what pinging sounds like but while accelerating there was small power dips every so often, but only while accelerating.

Could this maybe be because of dirty gas? It never does this on 87 octane.