Has anyone changed their oil viscosity from the recommended 0W-20 to a 0W-30 or 0W-40 when modified? I have the VAP tune, upper and lower pulleys and VAPs transmission tune. I am thinking of switching from 0W-20 to 0W-30 or 40, but wondering what others have done?

 

Do you have any data to go with that recommendation? There seems to be disagreement on this topic and I wouldn't necessarily trust what "many tuned owners" do.

My own recommendation would be to use the specified oil but reduce the change interval. Analysis of the used oil by a reputable service (I use Blackstone Laboratories) would let you know if the oil is breaking down or there are signs of unusual wear.

 

I think your instincts are the way to go here, but I’m one of these types that does not mistake a mechanic for an engineer. I’ve posted this before in other threads like this: I came across a video at one point where some guy made the decision to not use the recommended oil on his F-Type. At some point as YouTuber he somehow he found himself in a position to talk directly with Jaguar engineers, and he was told that the weight/spec of the oil is not an accident (duh), and that stepping outside the recommended oil is not consistent with the tolerances and engineering, could cause problems, etc…I wish I could find the video but I can’t…He stopped using improper oil…

It just amazes me some times how cavalier people are about just going against the recommended oil that is chosen for a reason, but people can do what they want. I think it’s an incredibly bad idea.

If I go into the hospital they’re not going to give me a blood transfusion with the wrong type of blood ;-0

In any case, this is the type of thing that comes up over and over, and that everyone has an opinion about. The only opinion that means anything to me in these conversations is the one coming from the engineers that designed the engine.

If I knew that a car did not use the right spec oil I would not purchase the car. That’s how strongly I feel about the topic. It would not surprise me if most of the reported engine issues out there are tied to not following the recommendations of the engineering.

 

I agree with this - lots of debate on this topic in multiple forums but not a lot of hard evidence that 1) you really need it and 2) it is not harmful for your engine. For my street driven engine that is mildly modded (I consider my stage 3 VAP 5.0 as mildly nodded), my opinion is that the OEM spec 0w20 is fine. I change my oil every 6 months or 5k miles, and I get an oil analysis every time. Always comes back healthy.

 

I'm debating trying a good 0W-30. I've stuck with the 0W-20 since modified (about 6K miles). The car is a weekend toy and short road tripper, I don't "beat" on it, outside of some highway pulls and the occasional pedal to the floor from a dead stop 0-60 type pulls. I change the oil every 3K miles or less so it might not matter much. I do get a UOA from blackstone every change (I think 4 UOA since modified) and there has not been anything concerning wear wise. The 0W-20 and 5W-20 just always seemed light for the power output of the engine, further exacerbated by the extra 100-125 HP and increased redline.

Next year I may go deeper into modifying the F-Type, most of the VAP stuff; larger VAP supercharger, methanol injection, aftermarket pistons and rods, maybe a cam, custom tune, ARP studs and other supporting mods. When the engine is out I'll really dig into the condition of everything. At that point I'd imagine I'm so far out of of design spec that I'll need to revisit this.

 

I am not expert here, but

1) it doesnt sound like you are putting a ton of heat stress on your motor. That is where increasing oil weight might be beneficial.

2) higher hp is less of a worry, high performance 20w oil can be fine for 700hp as long as you are managing heat. Especially ok if you are not cycling engine oil through things like hot turbochargers.

3) you could possibly see MORE concerning signs in your oil analysis if you move to a much heavier weight oil. Harder for the pump, harder to move through small channels, also possibly affect oil pressure driven mechanisms like variable valve timing.

I get your concerns, and moving to 30w is probably just fine, but (in my opinion) I am not sure I would try to "fix" something that isn't showing signs of failure.

 

It's neither catastrophic nor such a huge deal. In terms of why you would deviate - thicker can mean more wear resistance. I run stock oil recommendations as it's optimized for a cold weather crank (I live in Wisconsin).
Oil type is typically included in engineering assessment for your motor's clearances - bearing, etc. which is why it "matters". It's also well known CAFE drives the thinner oil specs that are being passed down.
This type of thread is very prevalent. I neither see supporting data (why would I, who runs dyno testing on their own car in the aftermarket), nor compelling enough evidence to suggest 1 or 2 step thicker weight would be meaningful in reliability testing.
It's the devil you know vs the devil you don't.

Regarding changing - I have inquired about this with others before. I also trust Swallows history as do a lot of UK users. They change oil spec on their stage 8 4.2L engine package, but leave 0W-20 for their modern AJ133 motor packages.
Anecdotal but Swallows has been in racing longer than most have been driving Jags.
https://swallows-jag.co.uk/performance-packages/

 

Yeah, lots of these types of threads for sure. Again, I really don’t see the need to add risk and go against what the engineering of the engine officially calls for. It makes no sense to me at all, but that’s me, and I’m aware that there are many opinions out there that don’t necessarily agree with the Jaguar engineers (for whatever the reason). If I had to hazard a guess these types do not know more than the engineers at Jaguar when it comes right down to it. As was said, a safer play is probably just upping intervals if someone has concerns.

At the end of the day it’s what people wanna do.

 

There are many people still holding on to "conventional wisdom" from the Old Days (before synthetic oil). I think that it'd be necessary to measure both temperature and pressure to be sure it there is a problem. If the oil gets too hot and pressure drops, I'd look to better cooling first. We've got a coolant/oil heat exchanger in the V of the engine. There is likely a larger one (more layers) available.

The used oil analysis I've been getting indicates the oil is in fine shape at my annual change with no abnormal signs at all. I'm sure if it were overheating there would be sings of breakdown (loss of viscosity, reduced additives) and if it were too thin the wear metals would go up. I'm going with science (empirical data) on this one.

 

Regards "Use what the mfg says": I use what the oil cap says, which on our early 2014 is 5W-20. Yes, JLR arbitrarily changed it to 0W-20 later....

5 points higher (thicker) won't hurt anything. But the Jaguar/Ford specs for oil (which the factory Castrol or Pennzoil Ultra Platinum DO meet) are important for engine longevity... the timing chains will thank you.

 

The difference between 0W-20 and 5W-20 is the cold rating. Both of those will have the same viscosity when the oil is hot. I suspect the change was not arbitrary, but from improvements in oil technology. It wasn't all that long ago that there was no 0W and we needed to be more careful on cold engines.

 

It's interesting that folks are claiming there is special engineering for these engines to run a 0W-20, yet JLR used to call for a 5W-30, then a 5W-20 on the AJ126 and AJ133. All while bearing clearances remained the same.

I wonder what changed? (Rhetorical question)

 

Well, like most manufacturers they don’t always necessarily get things right the first time and make adjustments I suppose. They have the advantage of being able to see what problems/failures are happening at a scale (that you and I don’t necessarily see). It’s almost as if you are suggesting that their change of course was totally random or something. I personally highly doubt that.

 

It's not random. It's just unrelated to bearing clearance.

 

The only explanation I have seen and yes it's a guess. Is that with all the timing tensioner problems and the advanced VVT setup Jaguar made that slight change from 5W-20 to 0W-20 in 2018. The bulletin they released is not specific as to why the change was made.

I have attached that bulletin plus an Engineering letter stating that the Pennzoil Ultra Platinum does meet the spec but they only give it a 2 year approval?
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The push for thinner oils isn't isolated to JLR. Take a look at industry recommendations across the board.

 

That change will provide better lubrication on cold start. Once hot, both oils will be at the "20" side of the spec.

CAFE is certainly part of the change, but improvements in oil allow it. Additive levels are still high at even my longest change interval to date, and wear metals satisfyingly low in all analyses.

 

It's the other way around. Modern oil formulas changed accordingly.

 

My statement didn't presume either way. I see it as a continuing process. My point was that based on empirical data I see no reason to use other than the current recommendations.

 

I'm pointing out the distinction because many seem to be under the impression there are risks to increasing the viscosity back to 5w-30 or higher.