I saw a sale on diesel oil the other day, and got to thinking.
1) My car specifies 20w-50 oil, which is hard to find in "gas engine" oil. I usually just run 15w-40.
2) The engine in my car started life as a diesel.
3) Diesel oil is really easy to find in 20w-50, and it's cheap.
4) Diesel oil has lots of zinc and phosphorous, which i understand is good for motors and turbos, but plays hell on cats.
I have no cat.
I can run diesel oil please?
Yes you may.
I do.
Oil in your engine is good.
You can mix oils and come up with something more appropriate as far as weight (as well as additive packages). Bob is the Oil Guy has a ton of information on this stuff and since you didn't name the oil in question that you're interested in...
5w-20 Penzoil could be used to blend down the 20w-50 to something a little more appropriate and still be low cost.
Also note that Item #2 isn't of interest, it's bearing clearances and oil pump differences and all that which we'd care about.
Get a cat. Why are you running 15w40 in any of your cars? What do you run in the winter, anything different?
I have used it for years without problems.
pres589 wrote: You can mix oils and come up with something more appropriate as far as weight (as well as additive packages). Bob is the Oil Guy has a ton of information on this stuff and since you didn't name the oil in question that you're interested in... 5w-20 Penzoil could be used to blend down the 20w-50 to something a little more appropriate and still be low cost. Also note that Item #2 isn't of interest, it's bearing clearances and oil pump differences and all that which we'd care about. Get a cat. Why are you running 15w40 in any of your cars? What do you run in the winter, anything different?
Getting a cat for the car isn't in the cards.
Item number 2: I'm pretty sure the clearances on this motor are "Close enough."
It's the F2T. I'm running 15w-40 in the car because the sticker under the hood says 20w-50 and most of the time it's easier to find 15w-40. I am seeing the oil pressures on hot days drop a little lower than i'd like to see, and i was planning on making the jump to 20w-50 to see how much better it was.
Noticed diesel oil was way cheaper, and figured i'd ask if it was a good idea.
Seems it is, so i'll be doing it. 
I'll probably keep running 15w-40 in winter in this car.
The rest of the cars get 10w-30 across the board... i think. Don't remember what i just put in the Miata. Might have been 10w-40.
Whoa, I never ran oil that thick in mine. I actually ran Mobile synthetic 0w-30 in the winter, conventional 10w-30 the rest of the year. I really don't remember such a label on my car that's odd, and seems excessive. What sorts of hot idle & cruise pressures are you seeing?
I think a lot of the advantage with diesel oil pricing is the volume, most are in gallon jugs instead of quarts, and I also shop that aisle instead of "car" oils most of the time. Depends what is on sale for the cars, the VFR gets a steady diet of 1 quart Suzuki 20w-50 conventional 4-stroke oil mixed with 2.33 quarts of Shell Rotella T6 5w-40. Seems like a decent package and I like the shift quality with that mix, something you don't have to worry about. In any case, it doesn't seem to sludge or change color quickly, whatever that's worth, I haven't ever sampled it seriously.
When I had a catless turbo car I always ran Shell Rotella. Flat tappet cam + ex-diesel turbo = happy.
Look at the API donut marking on the back of the bottle. Most diesel oils also have gas ratings—the opposite is not always true. Look for Cx/Sx ratings—C is for compression ignition (diesel), S is for spark ignition, and the second letter in each pair is the revision of the rating. Since the F2T is hardly a new engine, it was designed for oil ratings of long ago. Usually the dual-rated oils have an older S rating, but pretty much any S rating you'll find these days will do for your engine.
If memory serves, diesel oils also have a higher detergent content, and/or additives to control soot.
I ran diesel-rated 10w-30 Mystik in one of my old Escorts for a few oil changes. It wasn't much of an oil consumer before, but it stopped burning oil altogether after that, even when I went back to regular gasser oil. That's entirely anecdotal, mind you.
pres589 wrote: Whoa, I never ran oil that thick in mine. I actually ran Mobile synthetic 0w-30 in the winter, conventional 10w-30 the rest of the year. I really don't remember such a label on my car that's odd, and seems excessive. What sorts of hot idle & cruise pressures are you seeing? I think a lot of the advantage with diesel oil pricing is the volume, most are in gallon jugs instead of quarts, and I also shop that aisle instead of "car" oils most of the time. Depends what is on sale for the cars, the VFR gets a steady diet of 1 quart Suzuki 20w-50 conventional 4-stroke oil mixed with 2.33 quarts of Shell Rotella T6 5w-40. Seems like a decent package and I like the shift quality with that mix, something you don't have to worry about. In any case, it doesn't seem to sludge or change color quickly, whatever that's worth, I haven't ever sampled it seriously.
On the Rotella 15w-40 i'm using now, i'm actually seeing lower pressures then the 10w-40 Castrol GTX i was using prior.
But at the moment, i'm seeing about 15-17psi hot idle pressure, and around 35psi at 3000rpm cruise on the highway. It's safe, but i'd like to see 40-45psi at cruise.
Bear in mind this is a 195k mile motor.
ZDDP has been reduced in the more current diesel oils.
What car specifies 20w-50? Its been a while since I've looked, but can you not find Castrol in 20w-50?
spitfirebill wrote: ZDDP has been reduced in the more current diesel oils. What car specifies 20w-50? Its been a while since I've looked, but can you not find Castrol in 20w-50?
1990 Mazda MX6 GT.
I'm sure i could probably find the Castrol somewhere.... but not easily or on the shelves anywhere here. And diesel oil is cheaper. And apparently has things that turbochargers like.
I dunno where you are shopping, but my store offers 20w50 in all major brands, qts. and jugs, at identical prices to the regular weights.
BoostedBrandon wrote: I dunno where you are shopping, but my store offers 20w50 in all major brands, qts. and jugs, at identical prices to the regular weights.
Autozone, Advance, etc.... I ended up going to Walmart for the last change because the selection of heavier oils seriously sucks at the parts stores around here.
Rural King......buy yourself a 55gal drum of rotella diesel in any flavor you like....
Seriously, you'll be fine. And you haz better oil pressure than me, but I've got you beat at 3k....
12-14 idle, 50-52 at 3k.....
yamaha wrote: Rural King......buy yourself a 55gal drum of rotella diesel in any flavor you like....
I don't think i'll have the car for 50 more oil changes. 
I'm thinking about shimming the pump to see what happens.
i work at NAPA. our house brand full- synthetic is made by ashland oil (valvoline). it is available in 20w-50. it's also on sale next month for under $4 a quart. not sure about where you live.
The old rule of thumb was 10psi for every 1000 RPM off idle. I don't know if the F2/F2T are that different as far as oil pressure requirements but 32psi at 3500RPM doesn't sound so bad to me. I wouldn't go playing with the pressure release valve without better information on this thing.
belteshazzar wrote: i work at NAPA. our house brand full- synthetic is made by ashland oil (valvoline). it is available in 20w-50. it's also on sale next month for under $4 a quart. not sure about where you live.
Interesting.... i'm a little freaked out about putting synth in it though... simply because i know it's run dino oil for almost 200k miles.
Good price though... might be worth checking out, thanks!
pres589 wrote: The old rule of thumb was 10psi for every 1000 RPM off idle. I don't know if the F2/F2T are that different as far as oil pressure requirements but 32psi at 3500RPM doesn't sound so bad to me. I wouldn't go playing with the pressure release valve without better information on this thing.
Yeah, by rule of thumb, the pressure is fine. I'm just wanting to try the heavier oil to see if i can get the pressure a little higher before i really put the spurs to the turbo. (Need a new wastegate spring, got this one just about maxed out)
Engine in car started life as a diesel.
What is it now ?
My car calls for 20w50 as well. Never ever had any issue finding it anywhere I've been. Maybe you have a lot of old BMW owners in your area and they are buying it all up before you can get there?
In reply to iceracer:
Teehee! I mean it's derived from a diesel motor, i can even swap a diesel cam in it for moar powahs!
... a diesel cam as an upgrade? I had never thought of this. Is anyone else doing regrinds or new cams for these things?
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