Hey Peter, I've always found that a good rule to follow regarding octane is the higher the engine compression the higher the octane. High octane fuel burns slower which allows for a more complete combustion. Most engines with a 10-1 or higher compression require higher octane fuel because it burns slower and because higher compression engines will knock severely if the fuel burns to fast just my 2 cents 69 280 SEL 120,000 Miles 72 350SL 108,000 Miles 2004 VW Passat 4 Motion 1999 Mazda Miata -----Original Message----- From: Peter Frederick <[EMAIL PROTECTED]> To: Mercedes Discussion List <[EMAIL PROTECTED]> Sent: Thu, 19 Jan 2006 18:18:15 -0600 Subject: Re: [MBZ] Premium Gas or Not?
My rule of thumb on the octane issue is thus: If you have KE-Jetronic and no knock sensor, do NOT use anything but premium on the highway. Midgrade is OK around town, but you really need the knock protection on the interstate as the engine cannot retard the ignition timing if it knocks. Burnt valves is the usual result. On later models with LH-Jetronic and knock sensors, remember that retarding the timing will reduce both power and milage -- you will have to run both, keep accurate records, and decide whether the lower price is actually a savings for you own particular circumstances. I know that on several of my older cars, including my Mom's old Fairmont station wagon and the work van (with 300,000 miles on it!), the accumulation of crud on the piston crowns raised the compression ratio enough that regular rattled pretty badly. Premium cured the spark knock, and the increase in power and milage more than paid the difference. It is entirely possible to have the milage drop so badly from retarded timing that it's more expensive to run regular than premium. You also risk damage to the catalytic convertor/oxygen sensor running late timing on acceleration all the time. Peter _______________________________________ http://www.striplin.net For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://striplin.net/mailman/listinfo/mercedes_striplin.net ___________________________________________________ Try the New Netscape Mail Today! Virtually Spam-Free | More Storage | Import Your Contact List http://mail.netscape.com
