[MODERATOR NOTE] Yes folks, another oil thread. I'm letting this next batch thru as a courtesy to the posters and then that's it. The next couple of posts give good web references for your further study. As alsways, choice of oil has something of a religious aspect to it and no concrete answer will be reached no matter how many times it comes up. ---Dave In a message dated 7/22/02 6:18:49 PM Central Daylight Time, tomciodmc@xxxx writes: > Andy thank you for the explanation of "how oil works". I'm sure a lot of > people on the DML will benefit from reading it. But there is one thing I > don't understand. You say that you should change the oil every 3000 miles. > According to the DeLorean Owner's Handbook You should change it every 7500 > miles. Also most car manufacturers in Europe tell you to change the oil > every 15000km (about 9375 miles). So the question is, should I follow the > Owner's Handbook OR the guys that make and sell engine oil? (and are > interested in selling more) Tom, Perhaps the real question here is 'why push it'? The owner's manual for my 1990 Olds Cutlass Surpreme says to change the oil and filter and 3,000 miles for severe service. So did my 87 plymouth turismo. And that's not pennzoil writing that, it's GM and chrysler. I believe the general consensus in the united states is to change the oil and filter every 3 months or 3000 miles. Surely even if that figure is a little premature, at least you're safer than sorry, right? i've never heard anything about new oil being bad. what makes it better after it's been in the engine for a couple grand? surely oil with suspended particles is worse than fresh clean oil. it only seems logical, right? For the price of an oil change you can do yourself ($15??) i'd rather have the peace of mind that i've been maintaining my car the so-called right way than 'pushing it' as we say in the oil-change business. another thing people may not understand is the definition of severe driving. this is any time you drive in town with stop and go driving, in varying temperatures, constantly changing speeds, etc. severe driving really isnt that severe - it's everyday life in america. the only time you are NOT at severe service is if you live rurally, you start your car at the same time and temp every morning, allow it to idle for 10 min prior to use, you leave your driveway at the same speed every morning, you accelerate so many feet per second per second the same way each day, you reach a plateau speed and maintain it for so many minutues, you slow down at a certain rate, and then shut the car off. that is 'normal driving'. not practical, huh? > Being in that chemistry field a few years ago I learned that engine oil is > designed to work for a lot more than 3000 miles and it actually gets the > right properties after about 1000 miles! New oil is bad, old oil is bad. > It's the time in between when the oil is good. I've heard that the 3000 > miles figure came from oil manufacturers so they can sell more. To me it > makes no sense to change it so often. While it is true that the oil companies surely have a hand in determining the laws of preventative maintenence, why do YOU think it makes no sense? are you a lubrication engineer? i would just like to know why you personally think it makes no sense. what data do you base this attitude on? Beside hurting the engine the old oil > is one of the major sources of pollution. > Another thing is the time. Mineral engine oil should be changed every 6 > months (not 3) but no more than12 months. Synthetic oil can stay in your > engine for at least 12 months but no more than 24. > Same as above. where did these figures come in? don't you think that milage on the vehicle plays a bigger part than time? think of it this way. with time you have one factor - TIME. with milage you have many factors - temperature changes due to start up and operation, pressure changes, the continuing build-up of sludge, acids, deposits, and other suspended particles, and time. you say i am wrong with recommending a change every three months. why are you suggesting every six months? what data do you base this off of? while it is true that synthetic oil is certainly better for the engine if you go over on your oil changes, i don't think i would want to keep the same oil in my car for 24 months. seriously, i think that anyone who owns a DeLorean probably would rather stay on the safe side and stick with the norm - every 3 months or 3000 miles (for severe service). and you cannot afford to change it that often, one may want to reevaluate priorities! also, check out this page: http://autorepair.about.com/library/faqs/bl872a.htm?terms=how+often+to+change+ oil surely this thread will be killed before it comes to life! Andy Soma576@xxxx 1982 DeLorean DMC-12 VIN#11596 Fargo, ND 58102 [Non-text portions of this message have been removed]