Time (not mileage) Based Oil Change Intervals

[Hobbes]

I've done some searching but couldn't find any relevant info on this topic (my next step will be searching Bob is the oil guy site). My wife and I currently car pool to work. Since our Accord gets 11-12 mpg better, we normally drive it the bulk of the time (our commute is about 25 miles each way). While I cringe to admit the following to this particular audience, I only end up driving the Tundra about once a week and then around the house hauling brush and rocks. After putting 24,000 miles on it in the first year, I only put about 4000 per year for the last two. I use Mobil 1 and had been using 7500 mile change intervals when I was driving it regularly, although the last two have been due to time.

So if changing your sythetic oil has to be based on how long it's been sitting in your engine instead of how many miles you've driven, what would you advise my change interval be? You always hear 3000 miles or 3 months with dino oil but I'm not sure what is realistic with sythetic. Any feedback is greatly appreciated.

[gquenstedt]

I use Amsoil XL 5w-30, and the reccomended interval is 6 months or 7,500 miles, which ever comes first.

[wiseguy]

While I don't have an answer to your specific question, it does remind me of a situation I have always ponder. Suppose a new vehicle has sat on a dealer's lot for several months unsold: do they change the oil before it goes off the lot? No way, dealers are cheap. But according to the oil change schedules thrown around with regard to time, the oil should have been changed. So my conclusion, the time interval schedules are quite arbitrary and not meaningful.

[tempetom]

I go strictly by the mileage also, but it probably would be smart to change it after a year. I don't know what that does to the warranty but It wouldn't make sense to change it strictly by the calendar imo.

[akauth]

When you depart from normal, the best way to make sure that you aren't screwing up is to have the oil sampled when you change it. Either that or change it way more often than you really need to to be safe.

If you don't do a sample at least once, it's probably safe that you can change the oil once every six months and you'll be okay. You could do it every year and it would probably be fine too, but the problem is that if there is something going on in the oil - like you've got a lot of moisture due to lack of proper warmups- it will have more time to sit and do damage.

Personally, if you're running it at least once a week and it's getting hot enough to burn off any moisture, I'd probably change it once a year if I was running synthetic as a matter of habit.

I change mine once a year and I do oil samples, but I put about 12,000 miles a year on it and I also use synthetic like you. If I drove less, I wouldn't extend the change interval, I'd just change it at the same time.

With only 4,000 mile a year on the vehicle though - I think that age alone is going to play a bigger part in wear and tear on the vehicle than anything you're going to do by changing your oil intervals very much. Sitting is kind of tough on a vehicle but at least you're running it every week.


Alan

Originally Posted by Hobbes

I've done some searching but couldn't find any relevant info on this topic (my next step will be searching Bob is the oil guy site). My wife and I currently car pool to work. Since our Accord gets 11-12 mpg better, we normally drive it the bulk of the time (our commute is about 25 miles each way). While I cringe to admit the following to this particular audience, I only end up driving the Tundra about once a week and then around the house hauling brush and rocks. After putting 24,000 miles on it in the first year, I only put about 4000 per year for the last two. I use Mobil 1 and had been using 7500 mile change intervals when I was driving it regularly, although the last two have been due to time.

So if changing your sythetic oil has to be based on how long it's been sitting in your engine instead of how many miles you've driven, what would you advise my change interval be? You always hear 3000 miles or 3 months with dino oil but I'm not sure what is realistic with sythetic. Any feedback is greatly appreciated.

[KLS]

3000 miles or 3 months with dino oil

Very important for oil company profits. Dino oil is good for minimum 5000 miles or 1 year.

I'd use a one year oil change schedule for your Tunda. If you drive it enough each week to get the engine and oil thoroughly warmed, fine. If it doesn't get completely warm, change more often, or better, give the truck a good drive once in a while.


Ken

[ThomasE]

In a similar situation, I've cut my Tundra driving down to about 3 times per week and driving other cars that get better mileage. I'm also using Mobil 1 synthetic, and will be changing it once a year, probably putting on 7k miles per year now.

[Hobbes]

Thanks for the replies. Since I live in the boonies, the one time a week that I do drive is at least 30 miles each way, whether that be to work or church. Most often that will also entail some errands on top of that, so I know that I'm getting to full operating temperature. So far I changed the oil after 9 months and then just recently after about 13 months...I let that slip a little far. I have not done an oil sample in the past and may very well do one on my current oil as time progresses (I just changed it 2 weeks ago).

Other than the accumulating moisture issue, I was curious as to what happens to the oil to cause it to break down. I fully understand what happens during the course of driving it often, hence the mileage based intervals, but what about while it sits? I check my level often enough to prevent low levels due to evaporation (if it has some where to evaporate to) but am curious as to any other causes. I'm just now beginning to really research this issue in earnest....

[KLS]

Oil deteriorates very, very slowly when not used. It is mainly the high heat during operation that causes oxidation, plus nitration from blowby gases that damages oil. Eventually, the additives become depleted. I'd go two years in one family vehicle that gets very few runs, but runs long enough for everything to get warm.


Ken