On Fri, Jul 22, 2011 at 9:38 AM, Donald Snook <dsn...@mtsqh.com> wrote: > the car has a knock sensor and probably the computer will compensate, > but is that really desireable? I mean, if it was designed to run on premium > do we really want to have the computer compensating and lowering > performance? Is it really "designed" to run on premium? In other words, > is there some detrimental effect on the car running 87 all the time and > having the performance affected? (by the way, I think I just used both effect > and affect correctly in a sentence - but not sure).
This is an interesting topic and I think the answer to all the questions above unfortunately is "it depends." (Except for the part about "effect" and "affect"---Snook Esq. did indeed effect the correct use of both.) Whenever gas prices go up and the usual crop of stories about "here's how to save money on gas" pop up online and in the newspaper, one of the recommendations given is always "No car really requires high-octane gas; just put regular in and the computer will compensate; the engine will put out less power but you won't notice." This has always been Consumer Reports' position as well---they have gone as far to suggest that any manufacturer that says their car requires premium is pulling a scam. As some people on the list have noticed (Kaleb for one), the mid-'80s Mercedes engines that supposedly require premium---the M103 in the 300E, for instance---run just fine on regular, so they are apparently sophisticated enough to retard their timing correctly to avoid knock. On the flipside there are modern engines for which anecdotal evidence suggests that buying lower-octane gas is being penny-wise and pound-foolish. One of our family cars is an '02 Camry with the 24-valve high-compression V-6 used in a lot of Toyotas and Lexuses in the '00s (as well as the Lotus Elise!). Toyota says to use 89 octane minimum, which around here is midgrade. Right now regular is about $3.80 a gallon, midgrade is about $4.00; so that's a price difference of a little bit more than 5%. The car does run fine on regular. However, on midgrade, it consistently gets 10% better MPG (about 26 mpg highway vs about 23), more than making up for the price difference. I think the "just put regular in, you won't notice the difference" line of thinking is wrongheaded for a couple of reasons---first, you might well notice a difference for the worse if you worked out cost per mile, as in the case of the Camry I just gave; and second, if you're looking to save money and accept decreased performance, why did you buy a high-performance car to begin with? I'm reminded of the people who buy a Mercedes wagon, but then complain about the cost to fix the rear SLS and want to replace it with conventional springs and shocks. Alex _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
