What's the deal with high octane?

[Bimminator]

Can any one shed some light on the issue of high octane? My mechanic friend told me that my 1990 535i was designed to burn high octane fuel. I have since read some info that suggested that having been sold in Canada, or North America for that matter, the car would have been set up to run on regular and that it would have to be tuned to burn premium. I have noticed that the engine sounds better with premium but will it harm my engine as I doubt the previous owner did anything but routine maintanance.

Thanks, Shawn

[632 Regal]

with out a performance chip you need to run at least 89 octane. With a chip you have to use at least 91

[JonE]

It will run even better if you add an EAT chip with at least 91 Octane! When my '90 535i had the stock chip it ran 87 Octane with no problems, it's what was the required fuel octane. Now with the EAT chip I run about 92 Octane and the chip manages to produce more horsepower and torque as it optimizes the timing for higher octane fuel. I also get better gas mileage with the EAT chip.

[paul p (chi-town)]

with out a performance chip you need to run at least 89 octane. With a chip you have to use at least 91

Uh, sorta.
Dunno bout the M20/30 but the M60 takes midgrade (tho honestly it’s a rip-off, i simply get 93 for the better detergents), and the M50 takes premium.
As important is the quality for a given octane. Pay for brand name now or Techron (or more) later.

94 530iT&A ‘Helga’ (for sale...soon) --- 92 325i ‘Rolf’ (blown clutch) --- 91 Volvo 745T ‘Thor’ (13psi ).......”Hang up & Drive!”
”Bet that phone call doesn’t seem that important now, eh?” Nov 20, 2004

[bahnstormer]

if u have 9.0:1 compression like the m30 does it'll run on water =]
hehehe jk

but yeah the new honda s2k has like 11.5 to 1

and in europe the alfa's have upwards of 12:1....lucky bastards with 97 octane
at every pump =[

[Jon K]

if u have 9.0:1 compression like the m30 does it'll run on water =]
hehehe jk

but yeah the new honda s2k has like 11.5 to 1

and in europe the alfa's have upwards of 12:1....lucky bastards with 97 octane
at every pump =[

They don't have 97 octane at a pump, they have 97 or 98 RON... equivalent to 93 octane

[BigKriss]

yeah. same in australia.

[Kalevera]

Yes...like the owner's manual, and almost everybody else says, it's fine to run an m30 on regular/87. If you have a performance chip, it usually needs 91+ (that's the main reason why I don't have one...esp with the price of gas right now).

best, whit

[Bimminator]

Thanks for all the input I guess I was initially burning 93 for the cleaner fuel (ethanol blend) to help prevent carbon build up etc. but I haven't installed a chip yet so I guess I'll stick to 87, particularly because they are predicting high 90s upwards of over a dollar a litre for regular for gas this summer. Have I potentially done any damage burning 93 for the last six months or so?

Thanks great forum by the way interesting topics.

[peks]

dont think you can really damage it by running premium