2004 Jaguar XJ8 Mobil 1 15w50 ... need some advice

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StrateLOSS

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Hey all, I have a 2004 XJ8 w/79k miles located in NYC. I currently have PP 5w30 in the car w/ around 1700 miles. The 30 seems to be ,dare I say, "thin" . The motor seems to run very hot, and the compartment gets very hot as well.

The coolant was flushed twice last year after purchase, all gauges read normal. At times I get a slight rattle at startup, its very slight now with a pureone filter .

Yesterday I purchased M1 15w50 oil in hopes that it will both better protect and reduce heat to my engine in these VERY hot and humid times in the city. Heavy light to light traffic and plenty of short trips + idling made me think I need a heavier oil.

I remember reading on a thread about an oil burning M5 that this M1 50 weight is siiliar to a 40w... however since my purchase I've searched both through bitogs search engine and google (using www.bitog.com after my search) to search bitogs archives, and nothing but motorcycle oil is coming up.

So Id like to know if this oil will reduce under temps some, and provide adequate protection? I've never ran anything other then 5w30 in the car so IDK how it will react ( IDT itll be bad ) but Jaguar recomends using a broad range of oil weights.

Mobil did have its pour rates at such and such temp, but thats all a foreign language to me.

I read where it said as much info as possible to put on the thread, so sorry for the wall of text. Thanks in advance

-Vic
 
Well, it feels like it's hot in the engine compartment because of the effectiveness of the noise insulation / heat shield protecting the bonnet paint.

And you already know that Jaguar temperature gauges are not linear - the needle should sit one needle width below the halfway mark and this indicates the normal range of engine operating temperature. anything past that point is not just hot, it's way hot.

I used to run 15/50 in my V12, but frankly, I now run M1 10/30 in it and when I open the bonnet, much less heat rolls out. I'm having difficulty grasping the concept that NY can be hotter than Arkansas.I'm not sure that idling is hard on an engine.

The M5 oil burning woes I do not see as relevant to the AJ-V8. The AJ-V8 is not a defective design - the M5 engine certainly seems to be.

Personally, with 21st century oil, I would not go any thicker than M1 0/40 which will settle in and hold at a nice thick 30 weight. If all you are doing are short trips, the oil will be thick anyway - it will never get a chance to warm to operating temps.

So I would (and did) say no to 15/50 in my Jags.
 
hmmm, walmart had the 0w40 but it was the old sl rated...

I didnt mean to compare the 2 motors, just meant it as a reference point to the info on the oil. sorry for that.

I dont know arkansas weather but here it gets 90+ regular with alot of humidity. surfaces temps get well over 100 degrees on anything and everything, low winds, so the heat index is very high. The temp gauge reaches normal about .4 miles into a trip after about a 3 minute warmup...

would you know if the pour points are similiar between the 2 oils? I can exchange them as walmart is only about 15 miles from me ( in heavy JFK traffic ) , but I was planning on changing this oil out today..

Thanks for your post

-Vic
 
First off, what is the reccommended weight that Jaguar reccommends? Just curious.

I would think that a synthetic 30 weight like what you are using would do a better job than the 50 weight, unless you are racing it or have a turbo and a long OCI. Lubrication is a function of oil flowing towards and away from the part when it is replaced by oil flow, this action also absorbes and distributes heat, thicker oils flow a little more slowly.
You have to really heat up a 50 weight so that it begins to flow like a 30 weight, hence why it is used in racing applicaions. Or applications like long OCI's with a turbo where one expects it to shear a bit.

Thin oils circulate better and therefor provide a better coolign function.
It has been above 100 Farenheight and pretty humid here for the past week, I run 20 and 30 weights in everything but vehicles that tow large objects or a bus (the bus just died so that is a moot point).

If you really do have a overheating issues thing that cools the most is the coolant system. No oil in the world is going to protect your engine if there is an issue with the coolant system.
 
so theres no truth to the 50 shearing down to a 40 ?

I plan on finally stepping up to bi-annual changes regardless of miles.

once in june, once in october. est annual mileage is 9-10k.
 
15W-50 won't hurt a big Jag V-8. British engines always seem to do better on thicker oils.

I wouldn'tt go below a 40-weight in this engine, and if I had to choose an oil, I'd be using a 5W-40 HDEO. But since you HAVE the 15W-50, use that.
 
Originally Posted By: addyguy
15W-50 won't hurt a big Jag V-8. British engines always seem to do better on thicker oils.

smirk2.gif
 
yes thats true, but I would also be guessing that it isnt. I dont mean this to be a debate on oil temps.

My cooling system is fine, will this 50w be near a 40 ?

I picked this weight because I read its near a 40, I also drew the conclusion I need a heavier oil. Whether its to make me feel good or is necesary, IDK.

This car isnt an A-B commuter car for me, my Civic is. This is my leisure/luxo car for fun and long trips, so emotions matter on this one. My civic not so much, that will get w/e I have my hands on. Thanks for all replies

-Vic
 
I don't think anyone really answered the question about how thick of a 50-wt oil Mobil1 15W-50 is.

According to the datasheet, it's 18.1 cSt @ 100C. The range for SAE 50 is about 17-22 cSt, so it is on the thin side for a 50-wt.
 
Last edited:
If you are hearing a rattle at start up, take your car to a mechanic ASAP. IIRC, 1997-2004 AJ v8's had timing chain tensioner/guide failures. This occurs on both the primary and secondary chains. In late 2004 Jaguar started using metal reinforced guides to prevent cracking.

A slight rattle at start up is usually one of the indicators that the guides are worn/broken. I am not 100% sure of the exact model years affected, but I believe I am close.
 
thanks nate on the pour point.

the slight rattle at startup is due to the anti drainback valve on the filter. the car will sit for 14 plus hours before startup regularly. the chain tensioners were a problem on the 4.0s and not on the 4.2s.
with the pureone filter it didnt do it with gtx 5w30 HM, started sliightly with the PP. with an stp filter it did it everystartup. thanks I do appreciate the headsup but thats a non issue on the guides part.

the honda I am not worrying about the warranty... will the oil be good with a total mileage of 6k and and an age 9 months? my guess based on bitog posts is a yes ?
 
Originally Posted By: StrateLOSS
hmmm, walmart had the 0w40 but it was the old sl rated...

-Vic


That's not a bad thing.

Well, there are very good SM oils out there and yes as a whole the SM spec is better. But the SL versions of reliable brands (like M1) frequently are as good or better in demanding applications than SM oils.
 
404magnum I do understand that, I just dont know why I had a mental block and couldnt leave the isle with that oil smh... I need to get over a few things oil related and that I admit to, but slowly is how I can start rather then fullout.
 
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