Just gave the cat an oil change today. No difficulties, no surprises, until I went to the auto parts store to dispose of the used oil. I'd poured the old oil into the same container that the new oil came in.

So the guy opens the container, puts his nose to it, and says "has this oil been mixed with gasoline?". I said no, I had bought the new oil there, it hadn't been opened until the oil change today, and fuel had no part in the process.

He didn't argue about it...took the oil and dumped it into their bulk oil container. Before doing so, I put my nose to it also. I *may* have detected the scent of gasoline, but that could have been as much my imagination as anything.

I'm no mechanic, but I would think that oil and gasoline mixing itself in the engine is very bad news for me.

Thoughts?

John
1987 XJ-S V12
70,000 miles

 

Off the top of my head, my first guess would be a leaking fuel injector, stuck injector, or partially clogged injectors that don't properly atomize the fuel. Also excess fuel pressure or overly rich running.

In liquid form, the fuel runs down the cylinder walls and seeps past the rings.

 

Hi J_C_R

I've just been reading up on this and it seems that 'Mac' could be right about an Injector being Stuck Open, so possibly a good idea to take out all the Injectors and have them Cleaned and Matched or else get some Service Exchange Re-Cons

A bit of a PIA I know but cheaper than having to get another engine from somewhere

Interesting to hear what 'Greg' and 'Grant' think

 

It happens.

Injector loom failing can cause it, as the Injectors get confused and stay on longer than desired.

Small useage of the car is #1, the oil never gets to operating temp for that 1 hour, to "boil off" all the gunk that has accumulated, FACT.

Of course, Injector dribble, loom issues, FPR failure etc etc, will ALL cause running issues, but oil contamination due to the actual designed operation of the Internal Combustion Engine is NORMAL, and accepted.

NO damage to the beast, just the inside MAY be a tad cleaner due to the petrol washing things out, saves on Oil Flush products, HA.

Ask Greg about his adventures here.

 

Could simply be a few cold starts and the engine not coming up to temperature.

 

As a precaution, I would run some really concentrated injector cleaner through a 1/4 tankfull, and check the injector loom as Grant mentioned. I reckon the not-used-enough diagnosis above is correct, and the oil is not getting hot enough.
If you really have a stuck injector, believe me the car will tell you! Poor starting, clouds of "steam" out the back (actually pure petrol vapour), etc. The sump oil will come out like black water, but most of all, the engine will be wonderfully clean thereafter!
I found all this out in my early days when, not understanding the importance of renewing the injector loom (or I would have done so as a precaution) I had one suddenly short on me, and the car exhaust looked more like a steam train as I spluttered and limped home from the car wash, which was luckily only half a mile. But ever after the engine oil was clean as clean even after several thousand miles of use.

 

Interesting!

Well, the car is a daily driver, but since temperatures have just dropped here (we've had an unusually warm winter in the midwest up to a few days ago) that may be part of the issue. It has no starting or running issues and there seems nothing unusual about the exhaust.

I replaced the injector wiring harness (loom) when I bought it 5 years ago, not with a Jag part but hand-wired it myself. It's been out of the "V" since. I did use high quality heat-resistant wire.

Normally I can park it in a heated garage during the winter, but this year it'll have to sit outside until the end of April, so its got many a cold start ahead of it this winter.

I'll get injector cleaner into it today, and it seems time for either an oil pan heater or an "block" heater. Pulling the injectors isn't practical at the moment, since, as I said it's a daily driver (my ONLY daily driver) and I don't really have a garage to leave it in while the injectors are off for servicing.

Assuming that oil temperature is part/all of this issue, is an oil pan heater or a block heater going to be more effective for this particular issue?

Thanks,

John

 

John
I would forget about it. The car sounds fine, only use a heater if you are worried about it starting on cold days, otherwise no point to it. I reckon there is nothing at all wrong with the car. certainly no need to pull the injectors.
Lucky you driving it every day!
Greg

 

My post in much more detail got lost in cyberspace.

Short version :

Nose test inconclusive. Forget it.

try on oil drained cold. With care. Let it set a bit. If any gas in it, it should rise tot he surface and begin to vaporize. Light a match to it. If you get a flame, gas is present.
cold oil not liikely to ignite.

Add to causes. A cylinder or more that misfires....

Minor amounts of petrol will vaporize at engine operating temp. Oil temp enough to vaporize. The vapor will be removed through the the crankcase vent system .


Caveat: Issue in the vent system??? In USA cars, the PCV valve...

Carl

 

John,

I thought you did the loom a whole back, and as its a daily, it is just fine.

Heater etc for the oil, NAH, I reckon more gremlins than it will solve.

My X is the daily, and 25kms each way to work 5 days, so nowhere near an hour. If I dont go far on weekends, I change that oil at 3 months. 4 months if I do a weekend blast somewhere.
Wifes S is the same, she averages 2000kms per year, but oil change every 3 months.

I know I am strange, kids remind me constantly.

Oil is CHEAP, engines aint.

 

The V12 massively overfuels when cold, so it can take a while to get the oil up to temperature and keep it there long enough to boil off the gasoline. How long are you running the car when you use it every day?

When I was using a V12 as a daily driver, my average fuel economy in the summer on my drive to work ( averaged about 60 miles/day) was 16mpg ( imperial gallons), spring ad fall was about 18, as I was using less AC and winter was 10 mpg because the car sat outside all day at work. I did have a plug in available for the block heater, but the V12 still uses a lot more fuel in the cold until it is up to temperature. Fantastic heater though, I was never chilly in the car, even driving it in -35C weather..

 

Thanks guys...sorry for delayed response, but I ducked down to Florida for a week of golf. Got back the other day and after 9 days of sitting in the cold it started right up . It was on a trickle charger the entire time, which I'm sure helped.

I did put injector cleaner into it. I also changed the oil before I left, put 0W40 in it. While I was gone I ordered a heater to stick onto the bottom of the oil pan. Since this car is a "lifer", (either it dies first or I do), I just want to give the engine every opportunity to stay well lubricated. In any case I'll stop worrying about the gas-in-oil issue and just assign that issue to my imagination.

As an aside, I did take it in for a brake flush/fill today. My fluid was looking like pancake syrup, and the place I take it does a good job at a reasonable price and keeps me from crawling under it when the garage floor is freezing. Anyway, they mentioned that the differential (final drive) is leaking. I've always contemplated swapping it to something with a more "exciting" gear ratio, so it seems the time has come.

Thanks again for all the input.

John

 

Actually, the oil I put in was 0W20.

TY,

John

 

0W20 might be a bit light. Keep an eye on the oil pressure at idle and make sure the light stays off. The oil pressure on V12's is low at idle to begin with, so make sure it doesn't go too low.

 

Trickle charge a very very good idea.
0W oil an even better one.
As for the diff, you may find that the breather device is slightly sprung closed, mine was, and I modified it so it was completely open to air (with a circular flexible tube attached to prevent dust entry). No more diff leaks; but that assumes a decent set of seals; if yours have given up, output shaft seal replacement is pretty straightforward; input shaft not so much, but the diff itself, mechanically, is probably fine.

 

 

It is the winter and his weather is below zero. I assume we all agree the 0W part is fine? If so, is 20W too "thin" for the summer? I do not think so; the viscosity number is about flow, not protection to provide a "cushion" for the bearings. I seriously doubt a good quality 20 will provide any worse lubrication than an equally good quality 30 weight. I am very willing to be proved wrong, but getting oil to the bearing is all; the bearing pulls the oil through itself, like washing through a wringer - what evidence have we that a 20 weight oil protects better than a 30 weight over the life of the engine?

 

FWIW, and from the Jaguar shop manual....

15ºF and colder: 5/20 5/30 5/40
-5ºF to 60ºF : 10/30 10/40
15ºF tp 100ºF or higher: 10/50 15/40 15/50 20/40 20/50

There is considerable overlap, as you can see

Traditionally 20/50 has been the favorite among V12 owners. I use it until/unless temps drop below freezing and then go to 10/40

Cheers
DD

 

Heh heh, I don't know if "we" (hobbyists) have hard core evidence of anything.

I know that when temps drops below freezing my V12 labors a bit to turn over in the morning with 20/50 oil...but not with 10/40

I'm sure we all agree that oil starvation must be avoided and that flow is critical, especially at start up. And thick cold oil doesn't flow as easily as thin cold oil.

We can all probably agree that the V12s rarely suffer failures of the reciprocating assembly -- crank, rods, bearings, pistons. Almost unheard of, it seems.

Jaguar certainly gives us a wide range of acceptable oil viscosity. That must mean .....something.

As for engine oil and 'life of the engine', well, I submit that we'd need to take a dozen v12s, used identically for 150-200,000 miles but serviced with different oils, and never subjected to actual oil starvation, then tear them apart and carefully measure for any differences in wear, before drawing any conclusions. Or send in dozens of oil samples for analysis at regular intervals. Now that that majority of these cars are relegated to hobby-weekend-occasional use and driven maybe 5,000 miles/year or less.....well, you get the idea. This is why, IMO, synthetic and boutique oils probably offer no tangible, real world benefit to the engine and lots of benefit to the owner, if you get what I mean


Cheers
DD

 

Doug, I basically agree that whatever decent oil you choose makes naff-all difference; but I do like thin oil, as in 0W or 5W in cold climates - probably a case of " synthetic and boutique oils probably offer no tangible, real world benefit to the engine and lots of benefit to the owner". Still and all, this chart is pretty convincing on the cold flow benefits of low W numbers, and you can fill in your own preferences and compare! It basically proves there is no hot temperature difference between 0W 20 and 10W 30, but a noticeable cold temp difference.
https://www.widman.biz/English/Calculators/Graph.html
Also, IMO, the oil that was available when Jaguar wrote the specs for the V12 was a very different beast from modern fully synthetics, and cannot therefore be guaranteed to be the view they might take at present. Also the great Allan Scott did write in his XJS racing book that the Motul fully synthetics they had made a big contribution to preserving the engines when they were really getting hot in long races - not that we are talking about races, as you pointed out so correctly!
We must be careful, or this will turn into that perennial crowd-pleaser "which oil is best"!!