OCI advice

[Sam2000]

A friend of mine is coming up to a year on PU 5w40 Euro but just under 5k miles.

This is a 5 year old Mercedes with the 5.5L normally aspirated engine. The manufacturer interval is 1 year / 10k miles. The vehicle does see some very short trips but will get up to temperature once a week and get out for a good hour run a couple of times a month.

I'm suggesting 18 months / 7.5k miles. Perhaps do a UOA at that point. What do you think?

 

[Rolla07]

18 months 7500 miles seems like a good idea for a UOA. It should allow you to decide if an oil change every 2 years with just under 10k miles would work, and with this oil and car I would say it would be. Whats the oil sump capacity on this engine?

 

[A_Harman]

Yes, 7500 miles seems safe for that application.

 

[Quattro Pete]

Originally Posted By: Sam2000
I'm suggesting 18 months / 7.5k miles. Perhaps do a UOA at that point. What do you think?

Yes, definitely do a UOA to verify. In my case, I did 16 months and 6K miles on PU 5w-40, and did not like the results. Acidity was way up there. No fault of PU of course. It's the driving patterns that matter. If you have quite a bit of short tripping, especially during cold winter months, like in my case, then that's what you get.

 

[gregk24]

No, if manufacturer says 1 year / 10K miles thats what I would do. Sure, they oil might make it to 2 years, but if he wants to keep it long-term he should follow the owners manual.

 

[gfh77665]

I would go the 18 months and 7500 miles and change then, skipping the UOA. At that point its time to change anyways. Save the UOA money.

 

[il_signore97]

Originally Posted By: gregk24
No, if manufacturer says 1 year / 10K miles thats what I would do. Sure, they oil might make it to 2 years, but if he wants to keep it long-term he should follow the owners manual.


Yes, agree 100%. Mercedes recommends a maximum of 1 year OCI regardless of mileage. This is their way of ensuring that fuel dilution due to short trips remains in check.

To the OP... Remember, just because your friend burns the fuel out of the oil every now and then doesn't mean the damage that the fuel does to the oil goes away. Many times we see UOA reports with "no fuel" found, but we can see evidence that fuel was there in the form of depressed flashpoint, reduced TBN, a bit of extra wear metals in some cases, and obviously a reduction in viscosity. Therefore, even at once per week with a long trip, if it's not heating up on a daily basis, there could be traces of fuel sitting in the sump for a week at a time. I'm not sure how tolerable it is, but I wouldn't chance it if it were my vehicle.

I used to have a slightly modified vehicle prior to my current one, and I drove almost exclusively on the highway. My UOA's never showed any fuel as my oil was always changed hot after I got home (from a relatively long highway drive). However, I enlisted the help of Mr. Dyson at the time to chase what I thought to be abnormal wear. And he pointed out all of the signs of fuel dilution. Sure enough, after some investigation, it was clear the car ran rich and although the fuel didn't remain in the oil very long, the effects were still there.

 

[edyvw]

I still like old fashion rule: if you are not making big mileage, change oil before winter and again before summer.
Outside atmospheric changes, humidity etc, all that plays role in degradation of oil. Short trips, 7.5K in city, is like 15K on HWY.

 

[glxpassat]

I would go one year and always change it after the winter and save the cost of the uoa.

 

[HTSS_TR]

The sump capacity of 5.5L engine is about 8.5 quarts synthetic oil only. MB is going backward, they had fixed mileage/time for OCI more than 15 years ago, then they had oil life monitor (FSS) starting around 1998, and now back to fixed mileage/time.

I think many extreme short trips will kill the oil, I stay with 1 year if mileage is less than 10k.

Since changing oil and filter in a MB engine is so easy with a fluid extractor, I would buy one and DIY for any MB engine. The cost of an oil change or 8.5 quarts M1 0W40 plus a good cartridge oil filter is less than $60-70.

 

[G-MAN]

One year is plenty long for any oil. An oil change is cheap insurance on a rather pricey engine, IMO.

 

[bigt61]

8.5 quarts of PU 5W-40? Just change it every 10k miles and keep it topped off if it uses any. It will be fine.

 

[Volvohead]

Too many short trips.

One year.

 

[bigjl]

Another vote for maximum of 1 year.

If it was a turbo diesel with dpf i would likely do it twice a year.

My Pathfinder gets an OCI at 5k. Which is working out pretty much twice a year give or take a month or so.

The Pathy has just turned 120k and i picked up 8litres of Castrol Edge FST 5w30 C3 oil today for it at Costco. Unable to find the offer on Mobil Super X1 FE 5w30 i did last year. Castrol cost £60 for 8litres.

 

[riggaz]

Originally Posted By: Sam2000
A friend of mine is coming up to a year on PU 5w40 Euro but just under 5k miles.

This is a 5 year old Mercedes with the 5.5L normally aspirated engine. The manufacturer interval is 1 year / 10k miles. The vehicle does see some very short trips but will get up to temperature once a week and get out for a good hour run a couple of times a month.

I'm suggesting 18 months / 7.5k miles. Perhaps do a UOA at that point. What do you think?


Is he trying to save money or trying to extend his engine life?