Stupid Gas question
 

The thought just crossed my mind since Gas prices are ridicusously high. Even though most Mercedes cars require/reccomend PREMIUM grade gas, can you put in REGULAR and put in 1-2 bottle of Octane booster that claims that will boost your ocatene points by a certain number? WIll this have any ill effects or havea ny harm to the engine? Its Just a thought since I was working on my car yesterday.

If my math is correct, for a 15.5 gal tank, you would need about 2 gallons of 114 octane booster to raise a tank of 89 octane regular to 92 octane. Hardly cost efficient. Around here, premium is about 20cents more per gal, so an extra $3.00.

glenmore

...and I think a gallon of Octane Booster goes for about $14...

Octane booster is virtually worthless. Yes, many will run on regular (I do), or at least mid grade, but you may have to modify your driving style to avoid high load at low revs where detonation is most prevalent.

Also, detonation will be more prevalent in hot weather due to high intake air temp.

You didn't mention you year/model... whatever, you just have to experiment.

Duke

I've been able to get away with running regular in my 300E for most of the year, up until a couple months ago when it started getting really hot around here (near 100). Then I started hearing pinging, as Duke said, at low RPM with heavy load - usually when cruise was on, on the highway. I switched to midgrade as the temps went up, then eventually to premium. In a couple months I'll be able to start working my way back down to regular again.

Regular is fine in my car when the temps are regularly about 80 and below.

I was running fine on mid-grade...but switched back to premium when our temps went over 90... I will be back at mid-grade in a few weeks.

I think mid-grade gets me 1-2 more mpg

Make sure your engine has knock sensors if your going to use 87

These engines don't have knock sensors, but I, and many others have one built into our heads.

Air inlet and coolant temperatures are a BIG factor in the detonation equation. Since I only drive my Merc from Nov to June, when the temperatures are cool, I rarely hear detonation on regular unleaded unless I get caught in traffic and the coolant temp gets up to about 90C and air temp over 70F. Then I begin to pick up a little transient detonation on upshifts. The cure is to let if rev a little higher in each gear or don't get into the throttle too quickly in the next gear.

Based on past experience when I drove the car year round, even on premium I could get some detonation in hot weather.

BTW, if the coolant temp goes over 95C the EZL reduces timing slightly to help prevent detonation.

Duke

Thanks Guys. I have an 89 560SEL 150k miles. I will juts experiment.,

You can also save a little by mixing grades of gas, depending on where you live and the octane level of the gas sold in that area. Here in Indiana the octane levals are 87, 89 and 93. For a 16 gallon tank, using 7 gallons of 89 octane and 9 gallons of 93 octane still gets you 91.25 octane, above the 91 octane MB reccomends and saves 70 cents a tank. For the averedge driver a savings of about $30-40 a year. Or, one tank of gas now that premium is $2.65 here in Indiana. I havent changed from Premium grade yet, but maybe as tempatures cool I will.

-Brad

These engines being older engines, such as the M103 and older.

austin: 70 cents a tank?
 

if you're looking to save some more money , you could go to macdonald's and get their packs of catsup and squeeze them back into a bottle!that's gotta be at least 2 or 3 bucks right there.

No engines with the CIS-E fuel system have knock sensors.

Duke

Try selling and getting an older 300D...and run WVO no cost for gas anymore and better for the environment...and NO WAR NECESSARY!!!

I thought there was some difference in the RON ratings between Europe and the US which means the 89 octane US gas is actually the equivalent of European 90 octane?