Another thread on fluid additives tangentially brought up oil weight for best wear protection. That inspired me to do some research on what "meeting engine specifications" really means. More specifically, does "meeting standards" mean CAFE-driven emissions standards, or is it the very best oil for long term wear protection?
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I am not looking to debate the "morality" of car ownership, but rather discuss the best protection for our engine based on community data and knowledge. I'm assuming many are like me and just want their F-Type to last long enough to be buried in it.

My in depth research (AKA casual web browsing) has turned up some interesting stuff. First, I decided to compile an anecdotal list of similar high performance engines, and the recommended oil weights. The first is probably the most similar.

Mustang 5.0L - 5W-20
Mustang 5.0L Track Pack (via software) - 5W-30
Whipple SC recommended - 10W-50

Porsche newer - 10W-50
Porsche older - 10W-60

Corvette Z06 - Mobile 1 5W-30
Mobile 1's Z06 recommended - 0W-40

BMW - 0W-30 to 10W-40
Mobile's BMW recommended - 0W-40
Castrol Edge for M cars - 10W-60
Bimmerworld.com: If you notice more oil consumption we advise switching to a heavier weightoil that does not flow into the combustion chamber as easily.

Castro Edge for Supercars - 10W-60

(For contrast) Toyota Camry - 0W-16
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Finally, this interesting read shares my suspicion that a 0W-20 specification is more about avoiding fines and less about engine protection.

https://www.machinerylubrication.com...518/motor-oils

Question, what oil weight do you use and why?

 

Many of you Ftype owners might not even know that this engine was designed around 5w-20.
And JLR never changed its recommendation for this engine in multiple models. All of whom have had tremendous success with 5w20 for nearly a decade now, both in terms of wear and sludge/ carbon buildup.

What they did is suggested those who were using 5w20 continue doing so and specified the 0w20 on same exact engines after a particular year I believe it was 2013.

 

Yep, the original oil spec for the AJ133 was 5W-20 which was changed to 0W-20 some time in 2013 or 2014.
From my initial research I formed the opinion that this was wholly and solely to eke out another 1 or 2 MPG on the CAFE lab bench fuel economy test and had nothing at all do to with improved engine protection or extended oil change intervals.
Then more recently I read that the change was also to reduce the excessive timing chain/tensioner wear (which JLR are well are of), the theory being that a lower viscosity oil at cold start up got to these components quicker than a higher viscosity oil, especially where the car has been sitting overnight in very cold conditions eg 0 F or lower.
Anyway, I have never used 0W-20 and only ever used 5W-20 in both my XFR and F-Type.
Three reasons for that:
1. I live in a hot climate where the ambient temp in summer is often 110F+ and on only two or three days a year does it ever get down to around 30F and never anywhere near as low as 0F. So my engine doesn't need extreme low viscosity oil (0W) for cold start protection, 5W is plenty low enough.
2. 0W-20 is hard to find in my little backwater while 5W-20 is much easier to find and also much cheaper than 0W-20. Which helps as I change the oil every six months regardless of distance.
3. I really don't care about an extra possible 1 or 2 mpg and I would much rather have better protection from slightly higher viscosity oil.

 

Our 2014 V6's owners manual says 0W-20. But, the oil cap says 5W-20.

I have no issues with using 5W-20 of the proper (Ford) specification. (Which minimizes carbon buildup/effects)


If I were to research, I could probably find a Ford 5W-30 spec oil that would work OK, too.

 

I understand that 5W or 0W-20 might be the optimum choice for meeting mileage requirements with adequate engine protection. But IMO a best-mileage driving style profile is not going to be typical for a 550-650HP monster. I understand that cruising is all CAFE/Paris concerns likely consider, but what happens when you drive a 20 weight oil hard?

A lot of sources suggest severe engine wear/damage can occur when driven hard. The rule of thumb from 200F to 260F is each 10F increase reduces oil viscosity to the next lower 10 weight. IOWs, at +10F a 30 weight oil acts like a 20 weight, and so forth.

This seems born out by the supercar applications using 60 weight in otherwise daily driver engines.

 

First saw the 0w-20 mentioned in a TSB to VVT related startup rattle.
Got rid of my rattle and saw no need to change.
Did not change for 2 reasons.
1. I am a disciplined believer that there is no science like time-proven science. And the 5w-20 proved itself over 100,000 in several engines by 2013 and now 200,000 in many Land Rovers without sludge or chain or other lubrication problems. (0w-20 could be better, but the devil you know...)
2. 0W-20 will have more carbon buildup than 5w-20

Its easier for me to find 0w-20 than 5w-20 as Jag dealers were only buying one barrel and buying the latest.

 

Can you help me understand how or why the winter or startup rating affects long term performance? I know its never going to be exactly equal, but shouldn't we expect a 0W-40 and a 0W-20 to have the same warm-up performance, all else equal? And shouldn't 0W-20 and 5W-20 have the same normal operating temperature performance?

 

My understanding is that the "W" side of things is measured at low temperature and the other at high temperature. That would give both 5W-20 and 0W-20 the same viscosity rating at operating temperature, while the 0W-20 would be better for cold starts, especially in very cold weather. There may be a difference in longevity since they'd have either different base stock, different additives, or both, but that's speculation on my part.

 

Also, I don't think 100K miles is enough to claim victory from a modern engine. 200K is better. 300K+ isn't uncommon, I have a V8 truck with 330K and going strong. I wonder if manufacturers aren't reclaiming some if the advances in durability to both improve mpg and (only coincidentally, of course) invigorate their future sales pipeline.

 

Its where the significant majority of the wear occurs.
Its nearly metal on metal till oil flows.
There is almost no wear on the opposite end, where everything is lubricated warm and turning.
Old timers used to say 90% of the wear happens at start up.

But realize wear is an outdated topic. It used to be big, with replaceable sleeves and all. They dont even make rebuild parts for this engine!
Because reality is many other things will happen to it before it needs honing and rings and valves.
Plus even if a chain could do 250,000 miles without wear, (mine has done more on my v8 truck) you certainly would not trust the metal in such an expensive engine.
So its a replacement item at 125,000 miles even without wear.

 

​​​​​​I see. I use 5W-30 and am considering going to 5W-40 or 0W-40. So it should be no different WRT start-up performance.

My car has pulled timing on 5W-20 near redline. It hasn't done that since I added a pulley and went to 5W-30, but I attributed that to a little lower ambient. On both I lost a few tenths in the quarter mile to heat soak. I wonder if I switched back to 20 weight if the dyno would see the ECU pull timing again, but I don't want to hurt anything either. Maybe a 40 weight dyno and/or quarter mile runs would shed some light on it?

 

Can you elaborate on your reasoning in associating "pull timing" and 5w20 oil? Are you doing your quarter mile in 120F weather?

 

You guys should really look up the history of this incredible engine.

One of the things the engineers bragged about was reducing the size of the oil pump by making the passages narrower.

I dont know how that works out with thick oil and soot-loading.

 

im going through this as well with my XJ. the shop thats doing my oil change told me they're going to use 0W-20....and the local Jag dealer confirmed. is there no difference between using 0W and 5W other than cost?

 

While I don't know the detailed source of performance loss from one run to the next, its common among all drag racers to put the hood up and cool off from run to run to combat heat soak. I have seen the same thing on the dyno, as the later runs are always (in my case anyway) a few HP lower.

But the thing I was talking about, specifically, are my dyno runs where timing was pulled by the ECU above 5000 RPM. That can be seen here, the red line is from a previous dyno right after I had a smaller SC pulley installed and had not yet increased the SAE.

Apologies, I thought the difference was 5W-20 vs 5W-30, but the red run has Edge 5W-20 and the blue and green runs have Liquid Moly 5W-40, I checked my maintaince logs to confirm. The green and blue also have Racechip GTS Black.

The point isn't the higher HP of Racechip, it is the timing pull of the red line above 5000 RPM.

 

Yes, there is a difference. The 0W will protect better on cold starts.

 

It will flow slightly faster but will protect slightly worse. It's a trade-off beween flow and film strength. Water would pump even faster but would have no film strength.

 

Here is an old selection chart off autozone



What I get out of it is that 5W used to be considered too light weight to protect cold starts above 60F. And SAE 20 used to be considered too thin to protect above 80F.

 

This is slightly more believable than your unedited comment, but I don't think it's any closer to reality.

You're getting out of f that chart what you wanted going in. It's outdated in several ways. It looks like the chart I know from my the time of my first car, before the time of modern, synthetic oils. Read up here: https://www.bobistheoilguy.com/putti...nto-viscosity/

 

I believe you.
If thin oil protected as well its what we would use all the time, not just at cold start. the reason we dont want thin oil at operating temp is the reason you cite.
OEMs are fighting to keep startup emissions down (when they are atrocious) thin oil helps get cams and such online faster.