Hey guys, I've just got my 2014 DB9 back from an oil change from a local dealership, I know that the recommended oil on the owners manual is 0w-40 for this engine, but the dealer filled this car with 15w-50. When I asked on why they filled it, they replied that 0w-40 is too thin, especially with summer approaching. I'm currently at southern california and I know that summer is coming, but am i losing my mind to think that 15w-50 is too thick for this car? the car is currently running at 21k miles.

thanks



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Kevin

 

I have heard of 5w-40 being used. I live in NC and it gets very hot here. My DB9 currently has 0w-40 in it.

 

Interesting that they made the decision to change the oil specs for your car. I would at least document, with the dealership, your lack of comfort in their decision to make the change outside factory specs shown in your owner's manual.

 

ok. Noted! thanks

exactly, i was pretty bamboozled when they further said that 0W is for 0 degree & 15W for 15 degree when i ask why the change..... smh
but so far they've been pretty accommodating on my request to put on the recommended oil. will definitely update once it resolves

 

If they don't even understand oil ratings, then I'd be going somewhere else if at all possible. I personally wouldn't worry about using a 15-50 in the summer, but I'd definitely go to a 5 for cooler/cold weather.

 

Always interesting to start an "Oil Thread", www.bo
bistheoilguy.com is pretty much the "official" website for oil threads

These specs:

Cam Journal diameter (all) 26.962-26.936 mm (1.061-1.060 in)
Camshaft journal bore inside diameter 27.012-26.987 mm (1.063-1.062 in)
Camshaft journal-to-bearing clearance — standard 0.028-0.074 mm (0.001-0.0029 in)

Desired main bearing oil clearance is listed as .0015˝-.0022˝ (.038-.056 mm).

Determining the viscosity needed to support an oil layer between the metal parts is simple - what keeps them apart and keeps them happy. The parts are basically between 1.5 and 3 thousands of an inch apart. This is pretty typical for a stock, production motor. If it was a race motor these might go to 5 thousands of an inch.

In general the greater the clearance the thicker the oil. The thicker the oil, the harder to oil pump has to work to push the oil through the motor.

If a motor can tolerate a 0 weight oil (eg, the clearances are small) then that is the most fuel efficient.

I can't imagine needing a 15W oil in a non-race motor. My BMW E39 S62 engine specs 10W-60. I would think that a 5-20 or 5-30 would work well with these tolerances, especially if one was going 10K miles between oil changes on a motor that diluted the oil with fuel over time (IOW, what is the effective viscosity near end of life? That's what Blackstone's oil test is for!)

Note that the AM V-12 doesn't use bearings or replaceable plain bearings on the camshafts. Because they run at 1/2 speed and have relatively low loads, the heads are cast with high silica content in the journal areas and honed. In the case of the heads for my DB9, due to the prior owner running it on 6 qts instead of 12 they will need to be machined, chromed and honed to match the camshafts (which will be polished).

YMMV,
Larry

 

thats what i thought. Noted!

ok noted! thanks!

update: a rep from the dealership contacted me and says that with the 0W-40 they got a lot of engine issue (he didnt mention any specific issue), and hence the switch to the 15W-50 along with OTHER dealership. Honestly at this point I'm quite skeptical with what they said. I'm assuming that they are reassuring me that they did the right thing to avoid me asking to change the oil. thoughts? (pls correct me if im wrong )

 

In general the heavy oil takes longer to push through the motor at start up, and thus you run the risk of metal/metal contact. In hot weather it probably isn't an issue, but I'm surprised as this is something you go to at "end of life" on an engine (this will stop lots of engine issues, especially burning oil when the rings/valve guide seals are worn).

 

Exactly. the car is still sitting at 21k miles and 4 yr and doesnt consume any oil, somehow i find that the increase of the viscosity is somewhat unnecessary

 

From the owners book pg12.9
Engine oil: Mobil 1 0W-40. However if this oil is not available a fully synthetic 0W-40 oil meeting the specifications detailed below can be used. No other viscosity grades or specifications are acceptable.

I would be inclined to have them replace the oil with the correct spec.

 

yes exactly, the dealership didnt bring it to my attention that they arent putting in other oil that they like!

update: just spoke to other local dealership & overseas dealership and they've confirmed my suspicion that they are just saying that bull**** (summer need thicker oil, yada yada yada....) to avoid me asking for free oil replacement (i wanted the 0w40)
scheduled for the oil change + filter for next Tuesday. (from what I can tell, the manager wasn't too happy when i asked for filter replacement)

 

Most likely answer is that the dealership ran out of the spec oil so they used something close that they had on hand, not wanting to wait for the correct spec oil and thought you wouldn’t know the difference. Glad they agreed to an oil and filter change and hopefully they learn a lesson.

 

I would mark the oil filter with something to make sure they change it.