15w40 okay?

[Kai]

Thinking about swapping the oil out in my new red tubbie - the oil thats in there i think, is 10w40 but it seems a little thin. Oil pressure at idle is 40psi when cold, and at the first mark (20psi?) when warm, sometimes a little under. When its cold, the engine likes to rattle a little. Top end though - its not Rod Knock!

If i give it a little rev, then it quiets down. Is that cause the oil thats in there is too thin?

I bought a 5 litre drum of Castrol GTX High Mileage 15w40, for a bargain price today (£14.99), and was wondering - is this oil too thick for use in the 7M-GTE, or with its age, and 146,000 miles of use, will it be okay? Bear in mind that its started to get bitterly cold here at nights and during the day, it's not much better.

I've seen lots of threads about oil both here and the big oil thread on SF, but i'd like as near to a definitive answer as possible!

Cheers and TIA

 

[jdub]

Here we go again

The 1st mark at idle is 20 psi (on US cars)...what is your oil pressure at 3000 rpm, hot and cold?

For the miles on your car, a 40W is likely appropriate...your pressure at idle is actually good warm, but is on the high side cold. That tells me the oil you are using (10W-40) is a bit thick cold, especially for winter use. You want an oil that's as thin as possible at start...a 0W or 5W-40. Since those are kinda hard to find, a 0W or 5W-30 would likely be more appropriate for you in the winter.

Your motor is "rattling" cold because the oil's high viscosity cold is causing it to not flow well to where its needed. The oil you're using now is not too thin, but too thick cold. Putting 15W-40 in will make it worse.

 

[Kai]

Aah. At 3000rpm, cold, its just over the 40psi mark - doesnt really change a whole lot. When warm, its under the 40psi mark but not by much. At 2000rpm or so its midway between the marks.

The oil thats in there at the moment as i've just found out from the previous buyer, was a blend of two different oils, and looks to be piss thin

I did worry a little when once warm, the oil pressure sunk to the first mark - i've never seen the gauge go that low before. I know the system is a low pressure, high volume one - but once warm, the gauge sitting on the first mark is okay?

 

[jdub]

At idle, warm...the 1st mark is good, a bit high if anything...the TRSM says 4.3 psi or greater. Most high mileage motors show half what you have at idle. 40 psi warm at 3000 rpm is also in TRSM spec...toward the low side a bit, but still in spec. Not unusual for a high mileage motor due to the wear on the bearings.

Keep in mind, oil never thickens when hot...it thins to the specified viscosity in centistokes (cst) at a 100 deg C operating temp. Don't let the 1st number lead you into believing the oil is thin...that depends on the specs for the oil you choose. What you want is as low a cold viscosity possible to get flow as quickly as possible...then (when warm, at 3000 rpm) will give you at least the minimum 36 psi oil pressure per the TRSM.

The 10W-40 is doing that for you, but needs to have a lower viscosity cold...try to find a 0W or 5W-40. Or a 0W or 5W-30 that has a operating temp viscosity at the top of 30W spec...that would make it close to a 40W hot.

BTW - mixing oils is not a great idea...that's playing chemist with the additive pack.

 

[aye mate]

I run 15w40 in my 16x,000 7m-gte.

 

[jdub]

I run 15w40 in my 16x,000 7m-gte.

Good for you

How about posting the brand of oil and some pressures at idle and 3000 rpm, cold and hot?

 

[Kai]

Previous owner did the mixing, not me!

Just checking at halfords.com, the only parts store around, and they list Castrol Edge Sport 0w40 in a 4 litre can for £36.99 ($70.65). The only 5w40 is one for turbo diesel engines, but is the same price. The cheaper one is a 5w30 Castrol GTX Magnatec for £26.99 ($51.55)

 

[shaeff]

read this thread, and disregard the fact that the OP has a 1jz:

http://www.supramania.com/forums/showthread.php?t=35437&highlight=oil

-shaeff

 

[jdub]

Previous owner did the mixing, not me!

Just checking at halfords.com, the only parts store around, and they list Castrol Edge Sport 0w40 in a 4 litre can for £36.99 ($70.65). The only 5w40 is one for turbo diesel engines, but is the same price. The cheaper one is a 5w30 Castrol GTX Magnatec for £26.99 ($51.55)

Yeah, I know you didn't do the "blend"...just wanted to point it out, it's not a good idea

Here's the spec for the 0W-40 Castrol Edge Sport oil:
http://129.35.64.91/bpglis/lubtds.nsf/technicaldata/7272D91DF764EFF880257028004448EA?OpenDocument

Here's the spec for the Magnatec 5W-40:
http://129.35.64.91/bpglis/lubtds.nsf/technicaldata/A7289485B3DC4DC08025718B004F5E07?OpenDocument

Here's the spec for the Magnatec 15W-40 (couldn't find the one you bought...for comparison):
http://129.35.64.91/bpglis/lubtds.nsf/technicaldata/FE117C68F4D1DC02802570F8006690CE?OpenDocument

Viscosity at 40 deg C (in cst):
0W-40 75.7
5W-40 79.0
15W-40 110

Viscosity at 100 deg C (in cst):
0W-40 12.80
5W-40 13.20
15W-40 14.36

There's little difference "cold" at 40 deg C (BTW - that's pretty darn warm outside) between the 0W-40 and the 5W-40....a big difference for the 15W-40. Running a 15W-40 with it very cold outside is not a good idea if you like your motor...think it rattles now? Up the viscosity with that 15W-40 cold and you'll see what rattle really sounds like.

The 0w-40 is at the low end of a 40W spec...the 5W-40 is a little better....the 15W-40 is right in the middle of a 40W spec.

Since these are the oils available to you, based on the pressures you told me, and since you are looking for a cold weather oil...I would go with the 5W-40. It's a little thicker at operating temp and there is not much difference cold from the 0W-40. If you're concerned about it being a diesel oil, use the 0W-40.

This is why you want to look at oil spec sheets...the number on the bottle is only part of the story

Thanks Shaeff...I was going to mention that

 

[bwest]

Can we seriously get a sticky for this? This has been answered a lot lately...

another source (backing up jdub): http://www.mkiiitech.com/forums/viewtopic.php?t=898

 

[bwest]

I run 15w40 in my 16x,000 7m-gte.

I also run 15w40 in my 22x,000 international diesel...15qts of the stuff.

 

[edi]

i beginning to understand that it would be best to use 0W40/5W40 Viscosities durring the winter. what Viscosities would be good to run durring the summer?

 

[bwest]

the same. unless you are dealing with extreme heat issues (running your oil well over 212deg), your weight wouldn't change.

read this: http://63.240.161.99/motoroil/

 

[jdub]

edi - the oil that's "best" for your car may very well be a 30W multi-grade. It depends on what your pressure is at 3000 rpm at operating temp. You want an oil that gives you 10 psi pressure rise per 1000 rpm...due to the 7M oil system, that works out to be around 40-50 psi at 3000 rpm. The relief valve in the oil pump caps pressure at this level, unless there's a restriction in the system or you are using a viscosity that is too high.

The only reason I recommended a 0W or 5W-40 to Kai is he had good pressure at 3000 rpm (hot) with a 40W multi-grade already...the problem I see is when the oil is cold, plus the "rattle" he mentioned...I definitely would not use a 15W-40 in cold weather in his case. A full synthetic would be even better.

Read the thread Shaeff posted above and the one bwest just posted. Doc Haas is the most knowledgeable person I know concerning motor oil.

 

[aye mate]

Good for you

How about posting the brand of oil and some pressures at idle and 3000 rpm, cold and hot?

Shell Rotella T

Cars not currently running but from what I can remember about 25-30 psi at idle when cold and 15-20 psi when warm. 3000rpm was 40 psi, but the stock oiling system won't go over that because of the check valve.

 

[jdub]

If you been reading this thread...that's pretty high pressure at idle
It indicates a restriction to flow due to the oil's cold viscosity at idle.

 

[edi]

thanks, Jdub.

 

[Kai]

Aaah. Well, i bought it on the recommendation of other Mk3 owners in the UK and they said that 10w40 is too thin, and recommended 15w40. I bought the oil, but wanted to double check all the same.

I'll change it in 500 miles or so and go for a 5w30 magnatec with a new filter.

Not really much call to drive it hard around here - most of the time my driving is limited to the 2 miles to the store and back

 

[Nick M]

Aaah. Well, i bought it on the recommendation of other Mk3 owners in the UK and they said that 10w40 is too thin, and recommended 15w40. I bought the oil, but wanted to double check all the same.

I'll change it in 500 miles or so and go for a 5w30 magnatec with a new filter.

Not really much call to drive it hard around here - most of the time my driving is limited to the 2 miles to the store and back

I highly suggest you ignore everything else they tell you. That has to be one of the stupidest suggestions there is. And the internet is polluted with similar ideas.

Going 5W-30 is a good decision on your part.

Here we go again

Yeah, no shit.

 

[Kai]

I wont ignore everything they say, i think they were wrong on this issue. Then again, since putting 15w40 in, it sounds a lot better and pressure hasnt really changed much.

Like i said though - in 500 miles or so, i'll do a filter and oil change or 5w30, expensive though that'll be