Change intervals question - pandemic edition

[Eric_GM]

Hi folks,

I have 3 cars that for the past ~2 years have been rarely used ever since we were sent to work from home. In average each sees 2k to 3k miles a year. I do drive them at least 30 min once a month or more (not just a warm up). I recently changed the oil in 2 of the 3 cars after 1.5 years and it looked barely used (I always do it myself and haven't seen any milky deposits ever either). I'm not cheap and I don't mind changing it anyway for peace of mind, but I am environmentally conscious and I do hate accumulating plastic bottles and throwing perfectly good oil away. I've read other threads of people with classic cars that say that quality oils can hold up to 3+ years between changes. Is there any official word from manufacturers or independent testers to support that? There is a surprisingly lack of information available for classic/weekend toys/pandemic cars and such, especially from credible sources.

The hooptie fleet for context:
- 1978 Corolla with 400k miles or more (hard to tell, counter resets each 100k). Carbureted, 1.2L.
- 2003 Pathy R50, VQ35DE with around 130k miles.
- 1997 BMW E39 supercharged with ~120k miles.

I use full synth in all 3 of them and 10k+ miles filters. Usually stay with Royal Purple, Mobil 1 or Valvoline depending on what's available and the viscosities I need. I live in a year-round hot & humid place.

 

[tasch72]

I would recommend getting oil analysis done on the vehicles so you can have a more objective and factual basis to go off of.

We can help you bench race, but we can't be inside your engines to see how the engines are wearing, how the oil is oxidizing over time, and if there is any fuel dilution to account for, because looks aren't always everything.

 

[dadto2]

I go by miles, not elapsed time. In the event that some moisture condenses in the pan, the first good run on that engine will evaporate it back off anyway. I think you are at more risk of rodent or body rust damage than oil-related engine trouble when you let them sit.

 

[atikovi]

No need to waste money on oil analysis on hoopties. I go by how dark the oil is as to when to change on an infrequently driven car. If after 3 years it's still clear, I wouldn't change it.

 

[99Saturn]

Watched - I'm in the same situation. - One of our vehicles last saw and oil change in November of 2019.

 

[Hall]

Do what you feel is best for you. Your engines aren't going to get destroyed from oil-related issues.

 

[slacktide_bitog]

Change it every 2 years for low miles

 

[BMWTurboDzl]

Well some automakers (ex BMW) recommend an interval based on the lesser of 1 year or miles. Mobil 1 states their oils have a shelf life of 5 years so perhaps you could settle on a 2 yr interval? I imagine there's no hard and fast rule as it's probably vehicle and climate dependent.

 

[samven]

I was always a 5K or 1 year person but recently I have rethought that. I am putting such low mileage on my truck that at a year it may only have 1000 miles on it. I cant in good conscience throw 7 qts of good oil away just because it hit 12 mos. I do check it and give the dipstick a smell for gas and keep an eye out for any signs of oxidation, other than that I will run it till it hits 3k which is about 2-3 years. 3k is the book recommendation anyway for severe service.

 

[Johnmpb]

I go by miles, not elapsed time. In the event that some moisture condenses in the pan, the first good run on that engine will evaporate it back off anyway. I think you are at more risk of rodent or body rust damage than oil-related engine trouble when you let them sit.

This. I wouldn’t care one bit about time, just go by miles. Plenty of UOAs show oil sitting in the pan doesn’t really “deteriorate”

 

[Dave1027]

I've switched to a 3k OCI. That will put it about 2 1/4 years for me.

 

[Spike555]

I’d change it once a year and be done with it.

 

[Hall]

Mobil 1 states their oils have a shelf life of 5 years

Not trying to confuse the OP with my comment, but that 5 year shelf life is for oil in the original, sealed bottle (at least I'm 99% positive). Engine oil is exposed to dirt, fuel, air, and other contaminants.

 

[BMWTurboDzl]

Not trying to confuse the OP with my comment, but that 5 year shelf life is for oil in the original, sealed bottle (at least I'm 99% positive). Engine oil is exposed to dirt, fuel, air, and other contaminants.

Yes.

 

[Eric_GM]

Thanks for your replies, folks! I don't think there's a place where I can send oil for analysis nearby so I too go by looks and smell. The oil I changed in the e39 and the pathy was still translucent after 1.5 years and now after reading all the replies I feel bad I threw it away.

Unrelated but also true, rubber rot worries me a fair bit too, not to mention fuel going stale (I used to top them up but now I try to keep them around the half mark). The bimmer even needs a battery tender as it won't keep a charge after about 3 weeks.

I'm happy that I don't have to commute anymore, but it breaks my heart that the cars have been mostly relegated to grocery shopping and the occasional road trip.

 

[Matagonka]

No need to waste money on oil analysis on hoopties. I go by how dark the oil is as to when to change on an infrequently driven car. If after 3 years it's still clear, I wouldn't change it.

Come on, 3 years? Can't spare $20 to buy a jug of SuperTech?

 

[FordMan59]

I go by mileage and don't worry about elapsed time. The 5 year shelf life is nothing to worry about. All my cars are running just fine on 15-25 year old oil. My '97 Ford has 42K miles and has had 12 oil changes since new. For the first 30K miles I changed oil every 3K miles then went to 5K mile intervals. I think the last time it was changed was 2017 and has only been about 2K miles since it's last OC. It's used mainly for highway trips with the occasional drive to keep the battery charged but when it's driven locally it's usually run long to reach full operating temperature.

 

[atikovi]

Come on, 3 years? Can't spare $20 to buy a jug of SuperTech?

If it's been stored 3 years and the oil looks clean and was just changed before putting into storage, what's the point?

 

[Hall]

send oil for analysis nearby

Don't bother. It costs $25-35 for an analysis and you can change the oil and filter for that amount. Just change the oil if you were unsure about going longer on the oil.

 

[Drewby83]

Took me 18 months to hit 5k on my Tacoma due to pandemic working from home conditions. I dont see an issue going past a year with a low fuel dilution engine and synthetic oil.