Is it safe to put 87 octane in 1.8T?

[DruzeTito]

For the past 5 years i've owned my Bug I have been feeding my 1.8T with 93 octane but now obviously damn gas is getting expensive and iam pondering on switching to 87. What effects will these have to the engine?

[HeatherBug]

The car will automatically adjust the timing to compensate for fuel. However, you'll get better gas mileage and performance with 91+.

[noR]

no, it's not really safe for long term use. yes it will run. yes it will cause additional wear & tear.

[noR]

After doing more research I might rescind that 'will cause additional wear & tear' thing.

I'm still finding conflicting answers but best I can tell:

"Octane is a measurement of how much compression a fuel can take before detonation."

I don't get it really, since you could lower the temperature and expect to achieve higher compression before detonation, but maybe they have a set temperature they measure at.

I also find news that the temperature/speed at which it burns is not affected by octane.
... I'm not sure I buy that.

Prior to today's research, I believed:
higher octane is harder to ignite, but burns hotter & faster than lower octane.

That's obviously been brought into question; so I dunno.

But I do know someone tested both fuels in his 1.8t some 7 yrs ago. He found that the higher octane allowed him to achieve more miles per gallon. He also found that the exact numbers balanced out pretty evenly and at the time he found no advantage to using lower octane. It just flat took more lower octane fuel to go the same distance. just enough it happened, to match the price break.

This was 7 yrs ago by a 67+/- old man (where is beetlefritz?). I'm fairly certain 'high performance' was not his main objective.

[zeusenergy]

Originally Posted by noR

After doing more research I might rescind that 'will cause additional wear & tear' thing.

I'm still finding conflicting answers but best I can tell:

"Octane is a measurement of how much compression a fuel can take before detonation."

I don't get it really, since you could lower the temperature and expect to achieve higher compression before detonation, but maybe they have a set temperature they measure at.

I also find news that the temperature/speed at which it burns is not affected by octane.
... I'm not sure I buy that.

Prior to today's research, I believed:
higher octane is harder to ignite, but burns hotter & faster than lower octane.

That's obviously been brought into question; so I dunno.

But I do know someone tested both fuels in his 1.8t some 7 yrs ago. He found that the higher octane allowed him to achieve more miles per gallon. He also found that the exact numbers balanced out pretty evenly and at the time he found no advantage to using lower octane. It just flat took more lower octane fuel to go the same distance. just enough it happened, to match the price break.

This was 7 yrs ago by a 67+/- old man (where is beetlefritz?). I'm fairly certain 'high performance' was not his main objective.

When I first bought mine I accidentally put in 87... crappy performacne and I had to step on it all the time to go anywhere. So yeah, burns through fuel alot faster.
And the detonation (pre-ignition) problem is what the higher octane prevents. Our engines are on the edge of even running safely when on pump 91, you figure they have 75 horsepower per liter, that's pretty high. Toss in a "stage 1" software flash and we are around 100 HP/L. I think you are right about the higher the octane, the higher the flash point. Pressure and temperature are the enemy here, with forced induction involved the charge air becomes quite hot and dense, then it gets pressurized on the compression stroke... So the higher the octane, less chance of detonation, ergo higher flash point/harder to ignite as you say.
Search me on the formulation- no clue about that at all!
OP: Please just use 91 minimum! For your sake and the next owner's.
I used to work at a gas station (sunoco) and the owner always bragged about the fact people would buy the 87 because the 86 they offered cheaper was the same exact gas. Fuel octanes are allowed to be one grade off.
So if you see a gas station offering 86/87 or 90/91 you can pretty much bet they are the same. At least here in NH

[noR]

and if your performance goes down ... I would think it would come natural to use WOT more often.

And running WOT on a chipped car w/87 octane fuel... I don't think I'd recommend it. I'm not sure if retarding the timing would be all that's necessary to make it 'okay'.

You've still got the heat & compression problem.


(hhmmmm... the timing thing makes me think the different fuels DO burn at different speeds again... what gives)

[HeatherBug]

Just use 91.. That's what the manual and the gas cap says. You're not going to be saving any money by using 87... it's like a 10 cent difference.

[FlwrPwer]

Well, I understand where you are coming from....and Heatherbug, it's not a 10 cent difference. The difference between 87 and 89 is usually around 10-15 cents. Making the difference between 87 and 91/93 around 20-30 cents.

When I got my turbo I used 89. I caught a lot of flack from the people here on the forums for this, but i couldnt afford 93. I still got about 400 miles to the tank, and i shifted hard and at high revs. I had the car for 3 years, and nothing was wrong with it when i turned it in for my 07. I just wanted the triple white.

Many people here say different things. I asked the dealer and they said running the car on 89 would be fine. If you don't feel completely comfortable with 87, you can always use 89. Just my .02

[HeatherBug]

Originally Posted by FlwrPwer

Well, I understand where you are coming from....and Heatherbug, it's not a 10 cent difference. The difference between 87 and 89 is usually around 10-15 cents. Making the difference between 87 and 91/93 around 20-30 cents.

When I got my turbo I used 89. I caught a lot of flack from the people here on the forums for this, but i couldnt afford 93. I still got about 400 miles to the tank, and i shifted hard and at high revs. I had the car for 3 years, and nothing was wrong with it when i turned it in for my 07. I just wanted the triple white.

Many people here say different things. I asked the dealer and they said running the car on 89 would be fine. If you don't feel completely comfortable with 87, you can always use 89. Just my .02

I live in NJ, so maybe the prices are different for you and everyone else. It is between 10-15 cent difference.. But there is a Sunoco plant in my town so the gas is a little cheaper here. But like I said before, go by the manual.. They wouldn't print that stuff if it wasn't the best thing for your car.

[btb]

The lack of power is resulting from the ECU retards the ignition timing to control detonation. You'll get more power out of the engine by advancing the ignition timing (to the certain point). However, lower number octane gas tends to ignite itself instead of being ignited by spark plug(s). THis causes detonation and will kill the high performance engine in no time. Hence, you need higher number octane gas to be ale to withstand self-igniting.
IMO, car manufacturers put enough safe margin for individual sale region. For example, the lowest octane gas in the states is 85. Then a car should be able to run safely (not performance wise) when filling up with 85 gas. Engineers usually design system on the worst-case scenario. Assume that the car is factory bone stock.
Finally, I would say that fill your car with the lowest octane possible that will not cause detonation. It is harder to detect in today's computer controlled engine though.

[Too Cold NB1.8T]

Fuel with an octane level lower than 91 is alright for those who will "never" introduce their 1.8t to boost, however, I don't think this is likely, so, I suggest you stick with the correct fuel (91+ octane) or you could risk engine damage.

Oh yeah, I know, the engine has knock sensors, I wouldn't depend on them as a savior for using the wrong fuel because if one or both decide to fail at the wrong time, you might be serving toasted engine for a main course.

[btb]

Originally Posted by Too Cold NB1.8T

Fuel with an octane level lower than 91 is alright for those who will "never" introduce their 1.8t to boost, however, I don't think this is likely, so, I suggest you sick with the correct fuel (91+ octane) or you could risk engine damage.

Oh yeah, I know, the engine has knock sensors, I wouldn't depend on them as a savior for using the wrong fuel because if one or both decide to fail at the wrong time, you might be serving toasted engine for a main course.

Well said

[zeusenergy]

Originally Posted by Too Cold NB1.8T

Oh yeah, I know, the engine has knock sensors, I wouldn't depend on them as a savior for using the wrong fuel because if one or both decide to fail at the wrong time, you might be serving toasted engine for a main course.

"honey, what's for dinner tonight?"
"Oh, toasted engine."
"Mmmmm.... My Favorite!!"

[gringoloco2000]

Another consideration would be if you have a Turbo S with the AWP 1.8 or the non Turbo S with other engine codes. The AWP engines have higher compression and would likely have a greater need for higher octane to avoid detonation. I think it was .5 higher than the other engine codes.

[Yurko]

and avoid ethanol at all costs...