Are high mileage oils bad?

[audia6]

I have an Infiniti m35 which I use 0w40 in. But I have a valve cover leak which I will probably tackle later on because I have to replace the whole valve covers anyways (non replaceable sparkplug boot seals)

But question is are high mileage oils bad? I know they condition and swell up seals but always wondered if they would ruin seals in long run and swell seals that are not in need of conditioning ect...

Should I consider high mileage oil at 135k? Continue 0w40 or 5w30? To minimize burning oil smell from VC gaskets

 

[aquariuscsm]

Do high mileage oils have a stronger add pack? Like maybe higher moly,zddp,and a higher tbn? Only thing I know for sure is that they're usually a little bit thicker per grade from looking at the pds.

 

[CharBaby]

Well, it's best to change any gaskets that are reachable especially VC gaskets as they're mostly a DIY. But NO, high mileage oils will not hurt your engine. I've been using them in my '80 Firebird in my signature for many years, around the time of their entry to the market.

Just my opinion

CB

 

[Cujet]

High mileage oils are perfectly fine to use, even in new engines. Certainly some high mileage oils trend towards the higher viscosity side of the specification and that may be helpful in many engines. Especially if operated in hot climates.

I've not seen any significant seal issues with the use of HM oils. A while back, someone here claimed the o ring seal on his filter had swollen due to HM oil, and that when he switched back to conventional oil, the problem disappeared. O rings on filters are not the same material as crankshaft seals, and I've never seen an issue. I use HM oils all the time.

 

[951Indy]

I've used whatever HM oil is on sale since somewhere around 200K miles. It's at 356K now and still doesn't leave any spots on the driveway. Consumption went way down when I switched. I made the mistake of using a AAP special on Castrol Edge at 190K, and consumption went from a qt every 1800 miles to a quart every 1000 on the Edge. That prompted the switch and I haven't looked back. For top-off oil, I use whatever is left over from the other 7 vehicles I have. 0w20 M1 to 15w40 Prem Blue. I've even been using 15w30 diesel oil that was $3 a gallon on clearance. It doesn't seem to care for top-offs.

 

[MolaKule]

Originally Posted By: audia6
I have an Infiniti m35 which I use 0w40 in. But I have a valve cover leak which I will probably tackle later on because I have to replace the whole valve covers anyways (non replaceable sparkplug boot seals)

But question is are high mileage oils bad? I know they condition and swell up seals but always wondered if they would ruin seals in long run and swell seals that are not in need of conditioning ect...

Should I consider high mileage oil at 135k? Continue 0w40 or 5w30? To minimize burning oil smell from VC gaskets


Engine oil is formulated to condition seals, not gaskets.



Quote:
When discussing seals such as in engines, transmissions, and other driveline components, the context is that of using flexible, elastomeric materials to keep fluids contained within the mechanical system that has rotating components exiting the system, such as protruding rotating shafts.

For a gasket, the context is that of using a material (such as the silicone material you showed) or cork, or some other material to keep fluids contained in and around stationary objects, such as the valve cover gasket on an engine or the pan gasket on an automatic transmission.


Both seals and gaskets "prevent" loss of fluids.

 

[Imp4]

No.

 

[wemay]

Originally Posted By: Cujet
High mileage oils are perfectly fine to use, even in new engines. Certainly some high mileage oils trend towards the higher viscosity side of the specification and that may be helpful in many engines. Especially if operated in hot climates.

I've not seen any significant seal issues with the use of HM oils. A while back, someone here claimed the o ring seal on his filter had swollen due to HM oil, and that when he switched back to conventional oil, the problem disappeared. O rings on filters are not the same material as crankshaft seals, and I've never seen an issue. I use HM oils all the time.


This. No problem at all.