Engine oil sump size influencing your oil selection

[Jimmy_Russels]

Assuming a 6 month 5000-mile OCI with 50/50 city/highway usage for both scenarios I would do the following:
- My Volvo has a 8qt sump. I would put synthetic Supertech 5w30 without thinking too hard about it. With that amount of OIL vs MILES the oil will be perfectly fine, probably with very satisfactory UOA. Even the conventional Supertech 5w30/10w30 will do fine in that capacity, and usage.
- My friends Nissan Xterra has 3.5-3.8qt oil sump capacity on a V6. With that small sump, and OCI/usage listed above, I would only use Amsoil or Redline, most likely in 5w40/0w40 flavor. And even then the oil could be sheared quite a bit. From oils available on store shelves - Castrol 0W40, Mobil1 0W40, or Mobil1 15w50 if weather allows.

Why does more oil mean more mileage on the oil?

 

[Graham Piccinini]

Why does more oil mean more mileage on the oil?

A quart of fluid (in this case motor oil) has ~18927 drops.
Nissan Xterra will end up with ~66244 drops of oil.
Volvo XC70 will end up with ~147630 drops of oil.
Assuming the same exact time and mileage on both vehicles each drop of oil in Xterra will get more than double amount of cycles through the engine, as compared to Volvo oil drops.
As result that oil will be sheared more, contaminated more, oxidized more, etc.

It is a very, very, very rough overview... Endless amount of variables involved.

 

[Bryanccfshr]

Why does more oil mean more mileage on the oil?

Oil Additives are depleted with use. A larger volume of oil will therefore deplete at a Slower rate than A smaller volume in the same application. additionally there are the Benefits of slowing oxidation and wear Because it is a bigger heat sink which reminds me.

A Good analogy is a 2 gallon sink with 2 tsp of dawn vs a 5 gallon sink with 5 tsp of dawn. Which sink will Stop cleaning dirty dishes first?

 

[DGXR]

Oil capacity has no influence on my oil choice. I use what the manufacturer recommends with one minor exception: the truck is spec'd for conventional at 5k intervals, but I use synthetic and go 7.5k... it's mostly used for commuting and road trips, and spends plenty of time at full temp and highway speeds (4 cylinder with 5.5 quart capacity).

 

[Anduril]

Sump size never figured into the equation for me. Mustang gets 10w-30 because it has a rear main seal leak that I'm not going to bother fixing until it needs a clutch. A high-mileage 10w-30 stays in the crankcase well enough to not need a top-off between 5k OCIs. A 5w-20 does not.

XTerra gets 5w-40 HDEO because it spends a lot of its time either towing or off-roading. I get less valve clatter at startup with 5w-40 than 15w-40.

Motorcycles get 15w-40 Rotella T6 because it's cheap and JASO-MA rated. The other cars get what the manufacturer specifies.