Rate of Oil Consumption - Increases with Oil Aging?

[The Critic]

Not sure if this subject has been covered before, but has anyone else noticed oil consumption increases as the oil ages?

In this application and example, the oil being used is HPL - so I don't think viscosity loss is the driver. Other brands of oils have exhibited identical behavior.

It is a Subaru FB25 engine.

102,517 - Oil and Filter Change with HPL 10W20
105,217 - Add 3/4 qt of HPL 10W20
107,291 - Add 1 qt of HPL 10W20
109,051 - 3/4 qt low, Oil and Filter Change with HPL 5W30
112,479 - Add 1 qt of HPL 5W30

Basically, consumption starts out at 1 qt/3500 miles but increases to around 1 qt/2000 miles once the oil ages.

 

[racer12306]

Yes, on PP my Ram wouldn’t use any oil in the first several thousand miles. Then on the back half of the interval would use >1/2qt

 

[CR94]

It seems the opposite to me.

 

[buster]

Same thing on my Toyota and 05 Accord. Never quite understood why.

 

[paulri]

I've noticed the same thing on my Sienna & Highlander. I don't think it is viscosity either, as with my Highlander I lost 1.5 quarts (out of 5 qts, over 5K miles) but then had the oil tested, and it was still 20 (in grade). Twice the Highlander was tested (UOA) and no fuel dilution, so that wouldn't be the cause for my oil consumption.

 

[buster]

I'm thinking it has something to do with fuel dilution too.

 

[FZ1]

Not sure if this subject has been covered before, but has anyone else noticed oil consumption increases as the oil ages?

In this application and example, the oil being used is HPL - so I don't think viscosity loss is the driver. Other brands of oils have exhibited identical behavior.

It is a Subaru FB25 engine.

102,517 - Oil and Filter Change with HPL 10W20
105,217 - Add 3/4 qt of HPL 10W20
107,291 - Add 1 qt of HPL 10W20
109,051 - 3/4 qt low, Oil and Filter Change with HPL 5W30
112,479 - Add 1 qt of HPL 5W30

Basically, consumption starts out at 1 qt/3500 miles but increases to around 1 qt/2000 miles once the oil ages.

I think it's vis loss due to accumulated fuel exposure as the miles increase. Ymmv

 

[jetman]

Piston power aircraft I've owned are that way. Not much consumption during the first half of an oil change interval, then a lot more on the second half.

 

[doublebase]

Absolutely, almost nothing for the first 4,000 miles, and then a half a quart every 1,000 miles till I change it.

That’s what I’ve experienced in the past^^^. However now, nothing with my Toyota Avalon with the 2GR-FE.

 

[Blinker]

I’ve experienced this as well with PP and now QSFS. No oil consumption (dipstick level remained at FULL mark) all the way to 3,000-3,500 miles. After the 3k-3,500mile mark is when the consumption starts. Multiple different vehicles, I assume it has something to do with the natural gas base oil? I’ve not experienced this with other brands. I don’t plan on buying anymore SOPUS products.

 

[mt23]

I've experienced this with a few subarus. And the opposite, I've experienced more consumption up front and then tapering off after 3,000 miles.

 

[doublebase]

Probably should have mentioned that someone pointed out years ago that a contributing factor in this is that the actual shape of the oil pan (and most being tapered) would lead to what appears initially as little to no oil usage UNTIL the oil reaches a point where the taper narrows and the oil drop becomes more noticeable. If that makes sense. In other words, we are all using oil during the entire interval, it’s just not noticeable as quickly on the dipstick until it reaches a certain point in the oil pan.

 

[paulri]

That might explain this pattern of oil consumption in some cars, but not mine. I checked on parts.toyota.com and the drain pan for the 2 cars I checked has vertical sides, not tapered.

Probably should have mentioned that someone pointed out years ago that a contributing factor in this is that the actual shape of the oil pan (and most being tapered) would lead to what appears initially as little to no oil usage UNTIL the oil reaches a point where the taper narrows and the oil drop becomes more noticeable. If that makes sense. In other words, we are all using oil during the entire interval, it’s just not noticeable as quickly on the dipstick until it reaches a certain point in the oil pan.