Correct octane

[burn_your_money]

I have a 1985 Jetta Deluxe, made in Germany :D . Today I was looking at my gas tank cover thing and I noticed it said use 91 octane. Now I'm not 100% sure about this, because it was in German, but that's what it looked like. Are they being serious? Will 89 octane hurt my engine?

[jettadude]

they say it decreases the engine life, but for the car to run like it did at the factory use 91 or higher, and it is to prevent carbon build up and crap like that, you don't have to use 91 or higher, i use midgrade, which is i think 90 or somthing around there.

[Mortal_Wombat]

same I use 89 car doesnt ping at it doesnt seem to pull timing either

[burn_your_money]

That's a relief, 91 octane is like 95 cents a liter. I couldn't afford my car for long at that price.

[Mr_Diesel]

You need to use the gasoline that your engine was designed for.

[burn_your_money]

Ok I'm selling the car and getting a diesel

I remember back on JO I asked if running higher octane every 4 fillups like my mechanic suggests would clean the engine because it burns better. Everyone said it was just the additives in the higher octane, but from what I hear here it sounds like my mechanic was right?

[Mortal_Wombat]

that 91 on the filler flap is some euro rateing
the one we use is a little diff
(bro told me) these cars were designed for 87
but with age they seem to run better with 89
(carbon deposits on the pistons and stuff causeing pre-detonation)

and higher octane gases dont burn better they are just more resistant to burning from heat and pressure
he is right in that the higher octane gas MAY have more detergents in it
so i just throw in a bottle of injector cleaner every once in a while.

[Slalom]

that 91 on the filler flap is some euro rateing
the one we use is a little diff
(bro told me) these cars were designed for 87
but with age they seem to run better with 89
(carbon deposits on the pistons and stuff causeing pre-detonation)

and higher octane gases dont burn better they are just more resistant to burning from heat and pressure
he is right in that the higher octane gas MAY have more detergents in it
so i just throw in a bottle of injector cleaner every once in a while.

mortal got it right!
the gas flap on mk2's state they require "91 RON"... that's a european reference that equals 87 (regular) when applied to north american fuel ratings... have a read here:
http://www.btinternet.com/~madmole/Reference/RONMONPON.html

[burn_your_money]

Right on, looks like I can afford to drive my car :) Thanks guys. Higher octane burns slower tho doesn't it? I think I remember that from my aircraft operating course.

[Mortal_Wombat]

woot i was right :D

[ligur]

I have a 1991 Jetta CSX (1.8). The fuel cap flap says use highest available. I use 97 octane. Apparently it increases performance. Most of the sport cars here, like the Subaru Impreza use 97 as well, but the unleaded variation. South Africa only got 95 unleaded in about 1995 or so. Now with our newish fuel, Dynamic Unleaded, which is just fancy talk for 97 Unleaded, I have starting using it. British Petroleum (BP) near my office is the "only lead free site in the Western Cape". I have about 35litres of it in my tank at the moment. No problems as yet. Because I am doing such short distance now, about 8KMs per day, consumption has increased. Used to be about 650KMs per tank, now it's dropped to about 550KMs per tank. K&N drop in exactly helped. Got it when I was driving on the highway everyday on my way to work, doing about 140-150km/h.