Oil Change Interval - Why Time Driven?

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I bought a new compact utility tractor in November and wanted to make sure I bought some good quality oil for my first scheduled service. I did a lot of research and learned a lot about oils and filters, not just for my tractor but also for my vehicles and small gasoline powered equipment (tiller, lawn mower...).

I have always changed my oil (or paid someone to change it for me) using the severe duty schedule. I have used semi-synthetic 5w-30 oil (Motorcraft or Castrol) in my 2005 Ford Focus since new and conventional oil (Castrol GTX) in my 2002 Dodge Ram 1500.

I recently moved from MO to AL and live closer to work. In MO I was probably driving my Focus about 15-20k per year and expect to drive about 7-9k per year here in AL. My Ram has averaged about 10k per year since new. Yesterday (after going to 3 different WalMart stores) I purchased a couple gallons of Mobile 1 5w-30 Extended Performance. There was a sign in each store (and on the Mobile 1 web site) that said due to Huricane Ike they were having problems producing enough oil and supplies were low.

Now finally for my question, sorry if this has been covered before (I searched the archives and did not see this topic talked about). Why do oil companies tell you to change the oil at a certain time and/or mileage interval rather than just base the oil change interval on use (mileage or hours)? I understand they want you to buy more oil, but does the oil really need to be replaced at a certain time interval? I have seen many people state they change their oil at 12 months regardless of how many miles they drive.

I know many of you are doing UOA's and extend your oil change intervals to many thousands of miles over many years. On my Focus I think it would probably cost about the same to change the oil as it would to pay for a UOA, might save a couple $ doing a UOA on the Ram rather than change the oil. I would just like to go to the 15k listed on the bottle, even if it is say 2 years.

I have seen intervals from 3k/90 days to 30k/1 year. I have never changed my oil at 3 months just because (I am not sure I have ever heard of anyone doing this).

Thanks,
Jeff

BTW - If you haven't seen it, Mobile 1 is offering a $10 mail in rebate on 5 guarts of any Mobile 1 oil, limit 2 per household (if you can find it). That means you can buy 5 quarts of Mobile 1 for $16 (at WalMart after rebate) or $18.50 for Extended Performance. Rebate form is on the Mobile 1 web site.
 
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Mobil is the name, not Mobile. Mobile is a city in Alabama.

Car manufactures are the ones telling the owners to change oil/filter at a certain time or mileage interval, depend on driving styles, your car manuals have a section on when to change oil/filter. The severe schedule is usually half normal schedule, the severe schedule includes repeat shirt trips of less than 5 miles, extreme cold or hot, lot of stop and go ...

It's true that oil companies want you to change oil as often as 1k mile or 1 month, so that they can sell more oil and make more profits.


Originally Posted By: LeTempt

... Why do oil companies tell you to change the oil at a certain time and/or mileage interval ...
 
It might be because of moisture. When my wife just does short trips in her car, the oil fill tube gets pasty white with moisture in the oil.
 
The mileage interval makes sense, as engine ran oil and it's additives are used up and otherwise contaminated. The time issue is probably because of unknown storage and other enviromental things that they don't know about, leading to contamination of oil or changing chemisrty, so it's safe, easy, and cheap to simply change out oil. Other that a loss of money, no real issue with changing oil to often, but big possible issues with not changing often enough.
 
Mobil, funny I didn't catch that after typing it several times....I guess I was tired :
I use the service schedule called for in my vehicle operator's manual. Maybe I have just overlooked the time interval. I do know if you go to different oil company web site (Amsoil, Penzoil, and Castrol for sure), you will see a mileage and time interval. Penzoil even talks about their warranty and tells you 4k or 4 months even for full synthetic oil.

I can understand if you are in a cold environment and your trips are so short that you barely reach operating temperatures and there is not enough heat built up to burn off the moisture inside the engine. My Focus comes up to operating faster than any car I have ever owned. My Ram is slow to warm up, even in warm LA (Lower Alabama).

I would like to extend my OCI (using a high quality synthetic oil and filter) in order to save money and reduce the quantity of used oil that I generate. Of course I do not want to hurt my engines.

Thanks,
Jeff
 
This evening after dinner I went out and got my operator’s manual and maintenance schedule for my 2002 Dodge Ram 1500 and 2005 Ford Focus. Initially I thought that the normal schedule for both vehicles just required oil changes at mileage intervals, but after thoroughly reading the manuals I found where both vehicles specify mileage and time intervals for oil changes.

Dodge truck owner’s manual says this: In the maintenance schedule chapter the “A” schedule specifies an oil change interval of 7,500 miles or 6 months, whichever comes first. Schedule “B” specifies just a mileage interval of 3,000 miles. I thought this was kind of odd. Then I went to the section on engine oil in chapter 7 and it gives the conditions for schedule “B” and then specifies a 3,000 mile or 3 month change interval. Not sure why it doesn’t just say this in the service schedule like it does for the schedule “A”.

Ford Scheduled Maintenance Guide (covers trucks, vans, and cars) says this: the normal schedule for trucks, full-size vans, SUV’s, mini-vans, and cars specifies a 5,000 mile oil change interval. In the back of the book it lists “special operating conditions” and this tells you to change the oil at 3,000 miles or 3 months. Then there are a few pages recording special operating conditions maintenance and it looks like that is the end of the book, but there are 2 pages titled “exceptions”. The “exceptions” say for normal schedule the maximum OCI is 5,000 miles or 6 months and 3,000 miles, 3 months, or 200 hours of engine operation, whichever occurs first, for the “special operating conditions”.

I can see where someone could overlook the time interval in both of these owner’s manuals/service schedules.

Jeff
 
Well,he's from Alabama. Seriously,I would not go more than 12 months,but that's just me. You could change it every Fall.
 
Originally Posted By: LeTempt
Penzoil even talks about their warranty and tells you 4k or 4 months even for full synthetic oil.


I actually just emailed the pennzoil reps about when you should change PP on a car that's not driven very much. For my 3kgt VR4 that sees around 500-750 miles a year they said that it wouldn't be any problem at all to just change the oil once a year.
 
Originally Posted By: FZ1
Well,he's from Alabama. Seriously,I would not go more than 12 months,but that's just me. You could change it every Fall.


Good one...actually I am from IL, you know the cold place with the crooked politicians. Grew up in Southern IL where I lived until I joined the Army in 1984 at the ripe old age of 22. Moved all over the place and decided after I retired from the Army about 3 years ago in MO that I did not like the cold. I accepted a new civil service job in AL back in OCT 07. My (46 year old) bones got tired of the cold weather. Got pretty cold (for Lower AL) here last night, down to about 20. Supposed to have a high of about 70 on Friday though, much more like JAN weather is supposed to be :
Hopefully we will get started on our new (hangar) shop and home in the next few months and I am pretty sure I will get everything setup on an annual full synthetic oil change cycle except for my little experimental airplane. As I understand it, 100LL avgas and synthetic oil are not the best of friends unless you want to cut the OCI in half. It has a Limbach 2,000 cc type 1 VW engine and I have been running semi-synthetic for the last couple years with good results changing the oil every 50 hours (as recommended by Limbach).

I really enjoy this forum and have learned a lot.

THANKS!!
Jeff
 
I test drove a new 2008 Powerstroke that had 450 miles on the odometer. Based on when the dealer took delivery of the truck and the specified oil change intervals, it should be on its fourth oil change.

Maybe it's OK because those 450 miles were done in one trip, not around the block test drives. Yeah, you can warm up 15 qts. of oil in .6 miles. No problem!
 
The underlying assumption for timed intervals is that if you're not driving more than, say, 5K miles/6 months, then most of your use is for short trips -- more idling, not reaching operating temperature, etc...
 
.,..or ...you're operating in a manner that consumes much more fuel than mileage would indicate. This has sorta been expressed here as "stop and go" ..but that ISN'T severe. It's just he mismatch between fuel consumed and miles accumulated. In something like a taxi (or daily traffic jam commuter of short mileage) it sees VERY few cold starts (or small percentage of cold operation) and has none of the side effects inherent to "short trip" ..yet the mileage may be very similar to someone in a short trip situation.
 
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