Hey everyone!

My most recent oil change, I used 15W40 diesel oil in anticipation of a warm winter. I understand the differences for the most part, and I think the addition of zinc additives might be good, since I'm not burning any oil and the cat should be safe. It improved my mileage and I haven't had any problems during cold starts. Has anyone else done this and have I gone insane for putting cheap oil in my lovely Jag?

 

As long as it is a dual-spec oil you should be fine.
I switched to Shell Rotella T6 5w-40 at about 70k miles; now sporting 184k with no problems

 

It's not listed as dual-spec. I should have gone for the Rotella as well, and I will next time, but for a one-off perhaps the scrubbing agents in the oil will help refresh a few of the engine parts (one can hope!). 5W40 sounds perfect, I'll have to keep that in mind for next time.

 

About half way through this article are some comments about why diesel lube is wrong. That probably doesn't apply to dual spec, about which I know nothing.

The Truth About Oil, Part III | Performance & Hotrod Business

 

Your Jag doesn't really need high levels of ZDDP. The valve train does not endure the high loads of an OHV (pushrod) type engine where present day API SM oils may be insufficient.

 

Alright, hopefully it will be fine until the next change--I'll make sure to use dual spec or regular oil. Thanks for the helpful article, RJ.

 

What is the spec and brand of oil used? The statement about diesel oils not being suitable is vague and generally incorrect.

 

It's the tune-it brand from Wal-Mart. Unsure of the specs but I can check once I'm home.

 

From the Walmart site:

"TUNE IT! SAE 15W-40 PREMIUM DIESEL ENGINE OIL exceeds the requirements of API Service Categories CJ-4, CI-4 PLUS, CI-4, CH-4, CG-4, SM. Also is approved for MACK E0-0 Premium Plus, Volvo VDS-4, Cummins CES 20081, and Detroit Diesel PG0S 93K218 specifications; and meets Caterpillar ECF1A/2/3, MB228.3, ACEA E7, and MTU Type II requirements. Suitable for use in powershift transmissions specifying Allison C3/C4 or Caterpillar TO-2 fluids."

Note the API SM approval, so this is a 'dual spec' oil.

 

In general you should never use an oil that isn't rated for the service you intend to use it in.

I used to work for a company that made large compressors for natural gas pipelines, and the engines that drove the compressors burned natural gas. One of the customers was a big integrated oil company who had a policy of only using their own products. Only problem was they didn't make an oil rated for natural gas service, only gasoline and diesel. 2 of their competitors made a suitably rated oil, but they didn't want to use the competition's oil.

So they used their own oil rated for gasoline service, and the engine made it about halfway through the first oil change interval before it seized. The engine became scrap after that, it was so badly damaged. Unfortunately for them, it was close to a million dollars to replace the engine, so selecting the wrong oil was very expensive.

 

Not sure about the Canadian market, but the T-6 (synthetic) is offered here in TX by Walmart between $19.73 -$21.67/gal jug, depending whether it is on sale. Amazon offers a competitively-priced 3-pack on their "subscribe-n-save" program for $60-$70.
Shell offers $5/gal rebates (limit 2) periodically throughout the year.


Down here, you are a "ginger-stepchild" if you haven't a 3/4 ton diesel vehicle or larger.... so almost always available in any local Wally. Ymmv in locales where the F-Super-Duty doesn't enjoy such popularity.

 

In Canada T6 comes in 0W40 or 5W40 and is usually about $40 for a 5 liter jug.