How to interpret this oil viscosity chart?

[Varyk]

I have a 1980 Winnebago Brave. I'd like to replace my engine oil and found the recommendations in the owner's manual, but can't tell if the areas on the "recommended oil viscosity" chart are shaded in to say "use these viscosity according to temp" or "avoid this viscosity according to temp. Chart and page attached. Thank you for any help.

I'm in a 60-90 Farenheit temp range right now, btw

[R.Wold]

Generally speaking, in lower temps you should use lower viscosity so the oil flows more readily. In higher temps use higher viscosity to the oil doesn’t get too thin. However oil technology has come a long way since 1980, so a modern 5w-30 would cover you in nearly any conditions. But in an old 454, I’d still lean towards the 10-40, or at least 10-30.

So in this case, the shaded areas are the recommended viscosities.

[donr103]

Run 10w-40w all day long.. if 10 below run 5w-30w.. very few winter campers.. the real problem is people don't realize that most Chevy and ford chasss are just a light duty gasoline eng from their pickups put in big frames and forced to carry 20,000 or more.. so change all fluids.. very often.. flush coolant, brakes, power steering, trans, diff, ECT all of it!

Keep eye on colours of oil and Change it.. when it starts to change color... still major problem is people don't change fluids enough..

[Massparanoia]

What chassis is it on?

[Ray,IN]

Shaded blocks indicate approved oil for that temperature range. The engine may use more oil when the grade is lighter.

[ArtJoyce]

I like the 10-X0 range -10 to 110F I think I would be using 10-40 or 10-50 thinking its better at the higher temps. I would hope never to see -10.

[mitchoe]

Looks to me like 10W-40 would work well unless you get to 10 deg or less, in which case, move!

[NeilV]

Originally Posted by Varyk

I have a 1980 Winnebago Brave. I'd like to replace my engine oil and found the recommendations in the owner's manual, but can't tell if the areas on the "recommended oil viscosity" chart are shaded in to say "use these viscosity according to temp" or "avoid this viscosity according to temp. Chart and page attached. Thank you for any help.

I'm in a 60-90 Farenheit temp range right now, btw

On an 1980 Brave Class A Motor Home you would want the 10W40 or 20W40 in that temperature range leaning to the 20W40 or 20W50 if the coach has high mileage on it. The tolerances were not tight enough to use the 5W oils on those older engines except in extremely cold climates were it was well below freezing especially considering that on a Motor Home its running under the Severe Duty Cycle.

[SCVJeff]

Agreed. Its an old motor and works hard when its running. I wouldn't use less than 40W for any reason.

[GypsyR]

10W-30 has been recommended as the basic all around oil for cast iron V8's since the 1960's and well into the 1990's. It's been playing nice with my old Fords.
If you should decide to try a full synthetic oil, Mobil 1's 15W50 is the go-to for many a classic car owner. And for good reason. It has the additives older engines need that many newer oils may not. Has to be that exact one though, Mobil's 10w30 is a different mix and a better choice for late models. And surely lots of others you can use too, just that particular one has already been figured out and well tested by a LOT of people with older engines like ours (Chevy, Ford, Mopar, whatever.)

[Varyk]

I went with 10w-30 for the "all-around" description I've been reading about on various sites. My home is low mileage, 45k, I'm very curious about the comments recommending 10w-40.

What's the difference between 10w-30 and 10w-40?

[GypsyR]

Very little. If you watch your oil pressure gauge very closely when the engine is hot and then later change your oil for 10w-40 you might see a tiny bit more oil pressure when the engine is hot.