--- In dmcnews@xxxxxxxxxxxxxxx, "Tom Niemczewski" <tomciodmc@xxxx> wrote: > > ...the answer to that would be that whoever > wrote the Owner's Handbook must have made a mistake or just forgot to > mention that in YOUR book. I say "your" book because mine clearly states > that in the USA 87 should be used and that 91 was for Europe. Maybe I have a > later version of the book that was updated. > Anyway, in the Owner's Book that I have there is a mention of that on page > 40. Right on top, on the right side of the page. Here's an EXACT copy of > that: > > Fuel Requirements > USA > Your De Lorean is designed to operate at factory specifications at UNLEADED > GASOLINE only of at least 87 anti-knock index (R+M/2) (91 research octane > number) I have a 1983 Owner's Handbook. Probably the last edition printed. You are correct. It does state that on page 40. I however was referring to page 39 where is says: "Fuel Tank 51.6 litres 13.2 gallons (91 octane unleaded only)" When I see "91 octane unleaded only" in the handbook of an American car, I naturally assume they mean U.S. 91. That is a fair and reasonable assumption. Also consider that your average U.S. car buyer, like myself, does not know the difference between (R+M/2) & RON, so what is says on page 40 is over most people's heads. So take what it says on page 39, not understand what it says on page 40, throw in the "premium 91 is better than regular 87" marketing influenced misconception along with the common uninformed thinking that "I'm driving an expensive sports car, and expensive sports and luxury cars need to run on 'better' fuel" and you can see why your average DeLorean consumer would choose U.S. 91 octane to fuel their D. I now understand the difference between (R+M/2) & RON because I looked it up on Wikipedia. I also now see that the Owner's Handbook was poorly written. > Is this a bulletproof enough source? :) Yes, but looking back on what I wrote I was apparently not clear because I was referencing the desire for bulletproof sources on your claim of deposits building up due to using higher octane fuel than required that leads to emission issues when I said: "I don't believe using slightly higher octane than needed based on the engine's compression ratio will hurt anything..." > The higher the octane number the less chance for detonation but > at the same time combustion temperatures are higher. Okay, so wouldn't higher combustion temps burn off these deposits? Again, I'm not arguing as much as approaching this from the point of view of someone with limited knowledge attempting to apply common sense based on what they know. Also, my previous question still remains. If you have an engine that has been run for a long time on higher octane fuels than required, and it now has these deposits built up that have raised it's compression as a result. Wouldn't suddenly running it on lower octane cause, or run a higher risk of detonation since you're now running fuel lower in octane than appropriate for the engine's "new" raised compression ratio? I mean, if the deposits raised the engine's compression, wouldn't running a fuel that is not adequate for the current compression cause knock rather than clean out the deposits? > Use 87! Your car will be much better with it in the long run. Ambient air temp is another factor in detonation. I know this through experience, not through a text book. Again, I live in Phoenix, Arizona. One mile above hell, lol. I have a '97 T-bird with a 3.8 liter V6. It's a low compression engine too, and Ford suggests running it on 87 (R+M/2) in the handbook, but if I do on days between 80 & 115 degrees fahrenheit, or when climbing steep grades at any air temp, the engine detonates like crazy. I've had four Ford V6s that all did this, but when you ran them on 89 or 91 (R+M/2), there was no audible knock. Will the PRV V6 do the same? I don't know, but I also do not want to find out. > And the most important thing - 93 IS NOT BETTER than 87. It is if it prevents detonation in your particular engine regardless of what a handbook says. I'll take emission fouling deposits over detonation any day! By the way, just an FYI. Premium fuel in Colorado is 91 (R+M/2), not 93 (R+M/2). Dan W. VIN 16192 AZ-D To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/