How do manufacturers set oil change intervals?

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Seriously, how do they do it? My Fords call for 5,000 change intervals for normal service, 3,000 for severe. Nissan is 7,500 and 3,750 for the same designations. I hear Honda is 10K & 5K. Don't know about GM, and all the others. Seem like a lot of differences. I've read the Oil Change Interval formulas posted here and on the Synthetic Oil Life Study. They make sense, but I've never seen a rational explanation for the manufacturer's reasoning
 

driven2services

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They do oil analysis on the oil...and set the OCI as long as possible to make the engine last through whatever it is designed to last - usually around 100,000 miles.
 
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I think they just pulled some widely accepted numbers (3000-6000mi), until some of them got trapped with free maintenance deals. Then they start extending oil change intervals to save maintenance $$$ [Smile] [Smile] .
 
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quote:
Originally posted by ZmOz: They do oil analysis on the oil...and set the OCI as long as possible to make the engine last through whatever it is designed to last - usually around 100,000 miles.
I disagree. I think todays cars are designed for at least 200k miles of service. Some of GM's newer engines have significantly higher OCI recommendations than just 5 years ago due to new designs that dramatically change the amounts stress placed on the oil.
 

Patman

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I'm not so sure that they honestly do a lot of testing in regards to figuring out their OCIs. I'm sure they do a little bit, but I'd be willing to bet that we know more about how to figure out a safe OCI than they do! In a lot of cases I bet the engineers would tell their superiors that they figure a 7500 mile interval is safe, but then someone else decides to suggest 10k intervals instead, in order to make the car look more desirable from a marketing standpoint. A lot of people who buy new cars nowadays like the idea of having 100,000 mile coolant, 100,000 mile spark plugs, sealed for life transmissions, and also having much longer oil change intervals. A lot of people just find their lives too busy to worry about their cars, so they'd much rather buy a car where the amount of maintenance needed is the least amount possible. And since so many people lease a car and only keep it 3-4 years, car makers don't worry so much anymore as to whether or not the engine lasts 200k, since by that time it's on it's third or fourth owner anyways, and the original owner will have already gone through a couple of different cars, probably from the same maker, since people who lease probably also tend to be brand loyal, they just keep returning to the same dealer every 3-4 years.
 
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I am going to have to disagree on the previous points. From things I have read about the new Honda Accord (2002 and newer) the engineers that design and are responsible for these engines have carefully measured the output of the engine from a combustion standpoint and can tell that these extremely efficient engines are just not creating the amount of contaminents that they used to. Thats why you change the oil, to get rid of the contaminents. If the engine prodices less, then the oil should last longer. At the very least, I feel confident that they did not just go with conventional wisdom or pull the number out of the hat!
 

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Without a doubt manufacturers devote some time & resources to OCI's, but it all boils down to minimizing costs & increasing profits. A manufacturer specified OCI will weigh heavily on marketing. Car companies make money by getting new cars on the road & servicing them through their dealership networks. They want them to exceed thier warranty periods- not last forever! Joel
 
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What about Toyota and their 5w-30 at 7500 mile OCI? I hope they didn't put too much effort into determining that interval cause it is obviously too long for the sludgeomatic models!
 
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quote:
Originally posted by Patman: I'm not so sure that they honestly do a lot of testing in regards to figuring out their OCIs. I'm sure they do a little bit, but I'd be willing to bet that we know more about how to figure out a safe OCI than they do! In a lot of cases I bet the engineers would tell their superiors that they figure a 7500 mile interval is safe, but then someone else decides to suggest 10k intervals instead, in order to make the car look more desirable from a marketing standpoint. A lot of people who buy new cars nowadays like the idea of having 100,000 mile coolant, 100,000 mile spark plugs, sealed for life transmissions, and also having much longer oil change intervals. A lot of people just find their lives too busy to worry about their cars, so they'd much rather buy a car where the amount of maintenance needed is the least amount possible. And since so many people lease a car and only keep it 3-4 years, car makers don't worry so much anymore as to whether or not the engine lasts 200k, since by that time it's on it's third or fourth owner anyways, and the original owner will have already gone through a couple of different cars, probably from the same maker, since people who lease probably also tend to be brand loyal, they just keep returning to the same dealer every 3-4 years.
I see your point clear as day. I've been a used car buyer for the past two vehicles. I think I'm going to stick with new vehicles for now on. You just don't know what your going to get with a used car now a days.
 

TC

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It appears that one intent in implementing the latest North American oil grade (API "SL") was to standardize 7,500 mile oil change intervals. http://216.239.57.104/search?q=cache:B7xkRSXO4j4J:www.npinc.com/0004freeoil.pdf+api+sl+oil+change+interval+7,500&hl=en&ie=UTF-8 I agree that tighter engine tolerances, advanced engine seals, and better oil base stocks have allowed for an increase in oil drain intervals. http://www.canadiandriver.com/articles/jk/at_011128.htm [ December 28, 2003, 11:47 PM: Message edited by: TC ]
 
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[Cool] I had a job at an Oldmobile/Cadillac dealer in the early to mid 80's, and back then the manual said 7500 mile OCI for "regular service". Even the 3.8 V-6 that held 4 quarts with a PF-47 filter the size of a Dixie cup. [I dont know]
 
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One engineer was quoted as saying that the life of an engine is dictated by the amount of fuel that passes through it. One would imagine that the OCI would be dictated by how clean an engine combusts the fuel. I also think that it is some federally mandated (quietly) energy policy. Sunoco had to pay a big penalty (maybe it was Exxon) due to misleading advertisments about their premium fuel. The feds said that they implied that premium fuel was a benefit to engines ..which also implied that regular was not or less beneficial to engines. I imagine that the extension of the OEM OCI was a similar thing. That is, the manufacturers were conpelled not to "lead the public astray" with an unnecessarily frequent OCI ..or to even imply that one would benefit the engine if there would be NO BENEFIT over a predetermined "preferred" life cycle of the engine. Something like "the reliability or integrity of xx engine is not significantly enhance by doing 3000 OCI over 7500 OCI for 130,000 miles of use". They must have some "obligation" of reasonable assurence that the vehicle will not produce too much increased emissions due to maintenance related wear ...nor cost consumers any more than "reasonably necessary" to achieve that mileage. (do you get what I'm saying here??). [ December 29, 2003, 12:33 AM: Message edited by: Gary Allan ]
 
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From what I observed the last time I visited a GM testing facility, the process they start with is actually quite sophisticated. The hoops they have to jump through to meet/document all the EPA emission and fuel requirements takes a lot of effort and sophisticated equipment. However that is not to say that after the engineers' recommendations pass thru layers of management and MBA types things don't get loss in the translation or the goals are modified. Given the above, you may wonder than how did something like the Toyota sludgeomatic happen? Two theories I have is either it was a management decision not to modifiy maintenace intervals, or, maybe it was something like the overworked engineers in the trenches weren't aware of the specification changes between SH and SJ formulations when doing their testing since a lot of the testing is done year(s) before a model actually hits the showroom floor.
 
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My guess on the Toyota sludgemonster issue is that they made some changes (introduced defects, more appropriately) to the engine and didn't go back and run all the tests to see what the impacts might have been. A daily driver engine that can't safely go 5000-7500 miles on regular oil is messed up IMO. Of course, now people will say "AHA! 3000 mile oil changes would have prevented that". True, and wasted millions of gallon$ of oil on the rest of the cars that don't need to change it that often.
 
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quote:
Originally posted by John Smith: I think they just pulled some widely accepted numbers (3000-6000mi), until some of them got trapped with free maintenance deals. Then they start extending oil change intervals to save maintenance $$$ [Smile] [Smile] .
I agree [Frown]
 

Kestas

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When I was a young automotive engineer, I asked my mentors what criteria they use for coming up with a specification. They told me they simply find something that works and sounds reasonable, and perhaps has a history of good performance. Then they simply put the spec in writing and publish it. If it doesn't work, or something is amiss, they change the spec. There's no magic testing or controlled study they do to come up with some of the specs. Heck, even you or I could write some of these specs! Ever wonder why American manufacturers don't specify brake fluid flushes?... ever follow the story behind the Explorer tire pressure recommendations? Bottom line is specify, then make changes if the specification doesn't work.
 
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Kestas...that's really sad [Frown] I think I felt better thinking that the intervals were specifically designed to cause engine failure at mile 150,001 [LOL!] [ December 30, 2003, 08:36 PM: Message edited by: Matt89 ]
 

Kestas

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Perhaps not that sad. As you know, oil change intervals vary widely depending on how the car is run, i.e., is it run continuously on the highway, or is the car used for short trips and run only 2000 miles a year? In their defense, it's difficult to predict every variable for specification. The same is true for many other systems on a car. You'll have to admit though, if the general public followed the manufacturer recommended maintenance schedules, including severe service, there'd be significantly fewer "problem" cars on the road. That's why some manufacturers are experimenting with FSS systems. This is a new concept, and I'm sure the system will be tweaked with time. BTW, I get a kick out of reading the owner's manual where it recommends washing and vacuuming the car every week. Be honest - how many of us do that? [Wink]
 
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