10w40 recommended summer / 10w30 recommended winter by engine rebuilder?

Jonner · Sep 17, 2014

So I've had the 4.0L rebuilt in my '98 at one of the best engine rebuilders in Ohio, and I had a conversation with him about break in procedures and engine weights.

I followed his directions and am through the 20 minute break-in and 500 mile break-in. Now I'm getting into the normal oil change cycle of every 3000 miles. Since I don't have a garage, I'm calling around to local garages to schedule an oil change appointment.

I just got off the phone with one shop, and they acted a little strange when I said I needed 10w40 and a Mopar filter for my summertime oil change. Now, we are coming into fall, so I could probably use 10w30 anyway, but my question is does it sound out of the ordinary to spec 10w40 oil in a 4.0L rebuilt engine for the summertime? And 10w30 for the winter?

I know the FSM calls for 10w30 summer and 5w30 winter (but I forget the temperature thresholds off the top of my head).

Tony_SS · Sep 17, 2014

Why don't you ask the builder his advice?

iluv83vettes · Sep 17, 2014

http://www.aa1car.com/library/oil_chart.jpg

How cold does it get and how hot does it get? Not the car, but the air temperature.

Jonner · Sep 17, 2014

Tony_SS said:
Why don't you ask the builder his advice?

The engine builder's advice is in the subject - 10w40 summer, 10w30 winter. I'm asking if this sounds odd to anyone else familiar with this kind of thing?

87manche · Sep 17, 2014

it's not odd, but you're in NC. run 10w40 all year long.

you don't get cold enough to justify lighter oil in the winter.

FWIW I run 15-40W rotella year round. I'm certain that our week of -10 was colder than you'll see.

Jonner · Sep 17, 2014

iluv83vettes said:
http://www.aa1car.com/library/oil_chart.jpg

How cold does it get and how hot does it get? Not the car, but the air temperature.

The advice I got was based in Ohio - temp occasionally gets down to -10 F (-30 last winter with windchill) and goes up to 100 F.

I just moved to NC so I had I had to do some research. It looks like it gets to about 30 F in the winter with occasional, rare dips below that. Summers go up to 100 F.

Jonner · Sep 17, 2014

87manche said:
it's not odd, but you're in NC. run 10w40 all year long.

you don't get cold enough to justify lighter oil in the winter.

FWIW I run 15-40W rotella year round. I'm certain that our week of -10 was colder than you'll see.

I wish I could do my own oil changes! I'd do Rotella and a Mopar filter and be done with it!

So from the chart iluv83vettes posted, it looks like either 10w40 or the 15w40 87manche posted will work in this climate.

Tony_SS · Sep 17, 2014

Jonner said:
The engine builder's advice is in the subject - 10w40 summer, 10w30 winter. I'm asking if this sounds odd to anyone else familiar with this kind of thing?

Sorry, I missed that part.

Digger87xj · Sep 17, 2014

I see no reason for 10w40 in a 4.0. Especially in a fresh build. 10w30 is more than heavy enough. all the 10w40 is doing is sapping fuel mileage.

md21722 · Sep 17, 2014

Folks that have been doing this stuff for decades are probably old school when it comes to oil. I think 10w-30 year round would be fine.

sidriptide · Sep 17, 2014

10w30, 10w40, and even 5w30 are all fine for year-round use, really. the seasonal changes in NC arent drastic enough to require a seasonal change. i doubt the heavier oils will even give enough resistance to affect you fuel economy but i've never worried about that enough to try it.
if your engine guy is carrying a warranty on your engine, i say play by his rules and in the very least you will have less to worry about if you even have a problem. he's probably an old school guy, or learned from someone who felt seasonal changes were required.

myself, i'd would run 10w40 in the new engine thru at least the first 2 or 3 full mileage changes and then drop to a lighter oil. that is if i built it, or wasnt concerned with warranty issues.

Tim_MN · Sep 17, 2014

Everyone has an opinion, some are more correct than others. Use whatever weight oil makes you feel comfortable.

In Minnesota, I use 10w40 for summer and 5w/30 for winter. If the engine has excessive oil consumption, I will use 20w/50 in summer.

Jonner · Sep 18, 2014

Awesome feedback guys. The warranty issue is something to consider - 12mo 12,000 mile warranty.

I'll run the 10w40 for the first year, and then try out some 10w30 and do some mileage comparisons.

Right now it's got 30 straight weight per the break in instructions from the builder. I have plenty of ideas of what's right now.

Thanks so much!

Thehowler · Sep 18, 2014

My builder recommended 20-50 for the life of the motor.

Tony_SS · Sep 18, 2014

In my rebuilt engine I've been running 10w30 from day one. Mobil super 5000 dino. I have about 5k miles on it.

Talyn · Sep 18, 2014

10w-30 Valvoline VR1 in my stroker. I may change out to a 5w-30 though.

blondejoncherokee · Sep 18, 2014

I run 20w-50 valvoline VR1 in my renix with around 220K. It runs cooler in the 100+ degree summer days with this oil compared to the 15-40w. it was noticeable weekend over weekend going pushing it hard up the mountain to the trail. For the winter I run 15w-40 diesel , either rotella or mobil1. always wix filters.

87manche · Sep 18, 2014

md21722 said:
Folks that have been doing this stuff for decades are probably old school when it comes to oil. I think 10w-30 year round would be fine.

4 liters love rotella, it is also available in lighter viscosities.

you may think it's old school, but we have an engine design that is old school. It's not a DOHC 24v v6, it's a tractor motor. A sloppily built tractor motor with loose tolerances.

and for those that claim 15w40 is just hurting my mileage, my SWB MJ gets 25+ on the freeway and averages 21 combined every week, funny enough that's the exact same mileage it got when I drove it home from Knoxville with a crankcase full of 10w30.

Johnnie Walker · Sep 19, 2014

Jonner said:
Awesome feedback guys. The warranty issue is something to consider - 12mo 12,000 mile warranty.

I'll run the 10w40 for the first year, and then try out some 10w30 and do some mileage comparisons.

Right now it's got 30 straight weight per the break in instructions from the builder. I have plenty of ideas of what's right now.

Thanks so much!

If you plan on running full synthetic, The Valvoline VR1 (in the silver bottle) has ZDDP in it. Otherwise an additive is recommended.

The only way to know for sure what weight your oil is, is to send it to have an oil analysis done. Oillab.com or Blackstone labs.
If you look at test results of modern day oil, you will see that most are actually approx. a 10 weight at NOT.

Talyn · Sep 19, 2014

Amsoil also has some high ZDDP synthetic.

10w40 recommended summer / 10w30 recommended winter by engine rebuilder?

NAXJA Forum User

NAXJA Supporting Vendor

NAXJA Forum User

NAXJA Forum User

NAXJA Forum User

NAXJA Forum User

NAXJA Forum User

NAXJA Supporting Vendor

NAXJA Forum User

NAXJA Forum User

nobody of any consequence

Freakish Hand Strength

NAXJA Forum User

NAXJA Forum User

NAXJA Supporting Vendor

NAXJA Forum User

NAXJA Member

NAXJA Forum User

Piece of Fish!

NAXJA Forum User

Similar threads