So I just got my car back from my independent mechanic. This is my first time taking it to him and he's been in business for many years, working on a lot of different foreign and domestic cars including Jags.

So he changed the oil and put in Dextrol 5w-30 full synthetic. The owners manual calls for the 5w-20 with that weird WSS spec. He said that the 5w-30 offers more durability and more wear protection and that the WSS spec is only in relation to below freezing operating temperatures, which are normally sustained for a fleeting moment with the way the 5.0 heats up.

So I'm feeling a little uncomfortable running a slightly thicker viscosity but he assures me that many of the Jags they service with the 5.0 have been running as high as 190,000 miles on the odo using the Dextrol 5w-30.

Does anyone know if this is ok to use? Or should I take it somewhere else and have them out in the Castrol 5w-20? I just would rather not go through some type of catastrophic engine failure.

 

How much experience does your indy have with the JLR 5.0L engines?

Oil is cheap compared to the cost of an engine. Will that non-OEM spec oil cause your engine to seize up tomorrow? Probably not. Nevertheless, if it was my car, I'd replace that oil ASAP with the proper oil.

SUBSEQUENTLY ADDED - See my post #8 in this thread: https://www.jaguarforums.com/forum/x...stions-165571/

 

Thanks for the reply. The reason I took it to him in the first place is that I wanted to start doing 7500 mile intervals and figured going indy would be a good way to save on cost. Apparently now having him put in the wrong oil and now me having to pay somewhere else to swap it out is going to end up being more expensive than the change at the dealer, which I was trying to avoid in the first place.

Im not sure how much experience he has; in going to assume they mostly service the 4.2 based on what I saw in the shop.

I know there are a lot of 5.0 oil threads out there so I'm not trying to beat a dead horse (insert dead horse smiley here) but I just want to make sure it's worth my time and money to change it again. What are the downsides of having a slightly thicker oil at higher operating temperatures? Timeframe in which it should be changed? Very busy for the rest of the week unfortunately.

 

I doubt that anyone knows for sure, but it's your car, your decision. You know that the oil your indy put in your engine isn't ideal. If you're going to sell the car in the next 6 months, leave it in. If you plan to keep the car for several years, change it. The longer you leave it in, the more likely it is to cause problems. It's not just the thicker viscosity; it's the blend of detergents in the oil that are required to keep passageways clean. Bottom line: it's your judgment call.

Read my post #8: https://www.jaguarforums.com/forum/x...stions-165571/

 

Ok, so I gave up and called 2 Jag dealers near me (both from different dealer families) asking if running the full synthetic 5w-30 was ok. Here are the responses I got:

Service rep at first dealer: "I can't tell you specifically to use any other oil but the specially formulated 5w-20 that we sell, but I can say that I have never seen any engine failures or problems with the customers of ours that use a 5w-30, not that we'd have any way of being able to tell the viscosity were something to happen anyway."

Service tech at second dealer (where I get all of my service done): "As long as it's a full synthetic, you'll be fine. Just make sure that you change it at a closer interval, like 7,500 miles. It's ok to deviate from the required viscosity a little bit, just make sure you change it sooner because the oil can get a little thicker the longer it's in your engine. Try to change it sooner while it's still mostly viscous."

Long story short, I'm going to run with the Dexos 5w-30 for now and change my oil back to the specially formulated 5w-20 in about the next 5,000 - 7,500 miles. I drive a lot, so that'll probably be in about 4 - 5 months anyways.

Stuart, thanks for all of the input!

Also, I may want to add that strangely enough, the slightly thicker oil does seem to almost entirely resolve the rough idle issue I was having. I know many others were experiencing the same thing: https://www.jaguarforums.com/forum/x...esponse-83208/

 

You do realize that the guy was making this up as he went along, right?

Mechanics at dealerships are unlikely to have been exposed to enough real world examples to be able to draw such conclusions. It's hard enough for OEMs to do enough testing to prove something one way or the other never mind some individual. Refer to the first dealers answer- hwo would a mechanic know what's coming out of an engine?

Your indy was way off the mark with his 5W30 offering more durability and more wear protection comments.

 

Well, FWIW, I reckon that 5W30 will be perfectly OK. I suspect these oils getting thinner and thinner is more to do with engine friction and hence fuel consumption, than engine protection. Lets face it, your CAF law in the US means motor manufacturers have to concentrate on fuel consumption much more now.

 

Jaguar/Castrol co-engineered the oil specifically to meet the needs of the 5.0L engine. Read my post #8 https://www.jaguarforums.com/forum/x...stions-165571/
You can lead a horse to water, but you can't make him drink.

 

Well, after a lot of searching i found that Mobil 1 5w-20 does meet the Ford WSS M2C925-a requirement.
Check this out.
MOBIL 1 5W-20 | Mobil

 

a6kmita, from my understanding of things when it comes to viscosity, there are a few things that you need to keep in mind. Lets start with what the numbers mean. The first number is the thickness of the oil when cold (the 5W) and the second number is the thickness of the oil at temperature. So, really, when the motor is cold, both oils per testing should perform the same. It is when the motor is hot, that the difference comes in.

I am going to use extremes in this case to help make the point. You can decide where in the middle your situation may exist. A thinner oil (something with a lower number) is able to slide into smaller spaces than a thicker oil (one with a higher number). The thinner oil cannot build up as much of what is called an oil wedge (oil that is stuck between two surfaces and prevents the two surfaces from actually touching, think of sliding a wedge of wood between two things). So, a thicker oil will build up a better oil wedge and be more likely to prevent parts of the engine from touching each other. The problem comes in that newer engines are manufactured with much tighter tolerances than older engines. This means that a higher viscosity oil will have a harder time sliding into the small spaces and therefore may actually starve the two surfaces of oil, removing the oil wedge and leading to damage. This would be very evident if you were switching between say 0W-20 and 20W-50 oil. But, in the case of 5W-20 and 5W-30, the difference is going to be minimal as I see things. This is why you will find a lot of the older mechanics are more willing to use a thicker oil because "well, the older engines used to run on 20W-50 and had no issues, so, this thinner oil is just because some engineer is trying to squeeze out another 0.1 mpg out of the engine". While there is some truth to what they are saying, there is more to the internals of the engine and the tighter tolerances to minimize movement of parts and to make a motor last longer.

If you want to get unbiased information about oils, check out Used Oil Analysis - Bob is the Oil Guy. This is a guy that finds testing oils and the filters a "fun hobby". He calls a spade a spade and has no issues in telling things how they are. he has more oil analyzed by a professional chemist than I care to admit to. He has nothing to gain or lose by calling things as he sees them.

 

ding! Ding! Ding! Ding!

We have a winner!

 

I agree!




HOWEVER, back to the OP's dilemma......let me say this. The "recommended" Castrol Professional oil, that the dealer puts in your car is roughly $8/quart. The car takes 7.25 quarts, so they'll charge you for 8 (and if you ask, they'll most likely give you the partially filled quart, since you paid for it), so that's $64. The filter is about $20.


My oil change, and annual State Inspection, occur at the same time. For the state inspection, which is $21 by itself, and the oil change, they charge me something like $130-135, including tax. The car has the proper oil, and I don't have to get my hands dirty.


How much are you saving at the indy shop?

 

Indy will charge me about $90 for oil and filter where the 3 dealers near me range from $190 - $210 for the same service. I may just start doing fluids myself and leave the mechanicals to them.