jonus079

i was just wonder why i have to use Super grade gas (91 octane). i dont mind pay an extra $0.10 but what would happen if i used medium or low grade gas?

ML God

nothing really, if your vehicle starts to ping or knock, the knock sensor will retard the ignition timing so the knocking goes away. to you it will feel like a loss in power and performance. I would just stick to the 91

GDawgC220

i know some people who use 89 grade and nothing happens. Really, the computers in the car adjust for timing, so if you don't use 91, it retards the timing for the adjusted grade.

If you use 89, you can't feel a power difference, i've tried. I, personally, would never go down to 87, but i usually switch between 89 and 91 and the car is fine.

There was an article a few months ago regarding octane ratings for cars. Quoted from one MB spokesperson "if you don't use 91, you may not achieve the performance numbers specified for the certain vehicle".

I know sometimes betwen 89 and 91 can mean difference with price, as prices have gone up again.

-G-

sosh

Besides the power loss when the spark is auto retarded, there is the possibility damage from long term use. Excessive carbon build up, burned or carboned valves and possibly some piston damage from detonation. If you can't afford what MB reccommends you should have purchased a car that the mfg. suggests regular low octane fuel.

GDawgC220

While all that is valid, I don't think switching betwen 89 and 91 will cause damage, not in the manner that your suggesting. The detonation is retarded by the computer recognizing what grade is being used, so that is to prevent damage to the car.

It's each own's choice to put what they want in their cars. Some will follow precisely what to do, according to the manual and mfg recommendation, some will follow sometimes and some will disregard. What can ya do.

-G-

A good example are MB loaner's. Some dealers have old benzes and some give out new ones. I'm willing to bet most people who use those loaners refill with regular gas, not premium, cuz they see it's not their car, why would they want to waste their extra money on premium(91 or 93) when they can put in regular (87).

Stiggs

Dude....you're driving a benz. If you can't afford the gas, then don't drive it!!

Why risk it?? Just get the premium gas.....do you really want to take a chance on damaging the engine??
All that money you saved on 89 octane can be put towards your new engine!!!:p