My 1985 300D Turbo (CA version w/trap cat, EGR and ARV disabled) has had Mobil 1 oil in its engine, transmission, and differential now for awhile so I wanted to report to the group. There are all sorts of posts here about the good and bad things that happen with Mobil 1. Here's what I've seen so far.

Engine [Delvac 1, 5W-40] 2300 miles (mostly highway). No measurable increase in fuel economy (24-25 MPG highway, 21 MPG city). No leaks. No oil usage (or at least, none that I can measure). I plan to change oil at 5000 mile intervals now instead of the 3000 mile intervals I used for dino oil. Easy start after sitting outside all night in 17F (-8C) weather after one 30 second glow cycle, no engine heater or battery charger was used. Wish it had been colder for a better test, oh well.

Transmission [Mobil 1 ATF] 1300 miles (all highway). No leaks. No change in the 'firm' 1-2 shift (some have reported smoother shifts).

Differential [Mobil 1 75W-90] No leaks. No howling or other noise, before or after the change. (Squirt bottle form factor made adding the new oil easy, a plus.) Old oil was clean since it was new when I did the axle job about 7000 miles ago.

So I'm satisfied, except that the stuff is so bloody expensive. What have been your results and observations?

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

I just switched from Rotella 15w-40 to M1 0W-40 and drove it for the first time today. I do believe that it started much better this morning: almost instant ignition and no stumbling at all any more. Of course it was only in the lower 30's this morning, still I think it starts better than with the dino. I also gave the battery a good charge and replaced battery cables too, so it's possible that is also helping. I'm happy so far.

I am convinced of the value of good synthetics in gear boxes, transmissions and differentials, primarily for the potential fuel economy boost.

In IDI diesels where you are making some pretty serious soot, I prefer to run drain intervals that make synthetics un-economic.

I have also been doing oil analysis on a handful of various vehicles for years (and studying thousands of analyses from other folks) and cannot honestly say that synthetics give better wear numbers than good dino, in general.

I will say that synthetic motor oil is absolutely superior in extreme conditions, especially in the cold. That is where I would definitely use it.

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2009 VW TDI Jetta Sportwagon 172k miles (rear-ended harder than Elton John on 8/4/13. Total loss)

1991 Volvo 240 142k miles (T-boned by a stop sign runner. Total loss)

Synthetics also don't leave deposits behind like dino oils do and they definitely stand up to heat better (like in your turbocharger). Oil analyses don't tell you the whole story.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

What dino/interval/conditions are you running that created deposits?

I have run nearly a million miles on dino without deposits. And that includes dino in a '98 Sienna (162K and counting), a supposed sludge monster.

None of todays SL or SM dino, used with common sense in a sound engine, will leave deposits. Your statement makes it sound like dino oil leaves deposits as a rule. Am I mis-reading your post?

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2009 VW TDI Jetta Sportwagon 172k miles (rear-ended harder than Elton John on 8/4/13. Total loss)

1991 Volvo 240 142k miles (T-boned by a stop sign runner. Total loss)

With all that said, synthetic is definitely worth using for the 1)cold weather advantages- 2)additive packages which allow for long oil drain intervals.
Dino may very well be a viable choice for lube oil, however barely so, because you MUST change it every 3500 miles without exception. It is for this reason that I don't use it.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Generally synthetic oils stand up to heat better, that's a fact. Research it yourself. However, some engines may do fine on dino, especially older ones and/or those that are not turbocharged. Today's diesels all require synthetics. Why do you think that is? In Europe, hardly anyone uses dino oils anymore.

I know my wife's '93 Accord developed significant deposits on a lifelong diet of dino oils. Her car has been on synthetics for the past 2 years and hopefully her engine will get cleaner or maybe it already has. I haven't had the valve cover off to confirm.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I had a rear main seal leaking a little due to, not getting it quite right, when I reassembled the engine. The leak has almost stopped now after 30+K on Amsoil 15/50. I go 10K and add one gt between changes.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

I guess as a Chemist in the petro-chemical industry, you could say I have researched oil a little.

If you read my post with any care, you would see that I made a reference to the superior properties of synthetics at the extremes.

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2009 VW TDI Jetta Sportwagon 172k miles (rear-ended harder than Elton John on 8/4/13. Total loss)

1991 Volvo 240 142k miles (T-boned by a stop sign runner. Total loss)

That is absolutely not true. Many folks run Delvac 1300 and Delo 400 out to twice that distance with fine results. Many more don't, but could if they were willing to do so.

How do you explain the millions of autos that have run hundreds of thousands of miles on 5,000 mile dino intervals?

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2009 VW TDI Jetta Sportwagon 172k miles (rear-ended harder than Elton John on 8/4/13. Total loss)

1991 Volvo 240 142k miles (T-boned by a stop sign runner. Total loss)

1. Piston rings pushed way up on the piston (for better emissions) creating a heat situation at the ring that requires the already admitted superior thermal properties of synthetic.

2. The desire of automakers to extend drain intervals to show the prospective buyers how maintenance free their cars are.

This is not an indictment on dino oil. Merely recognition that in some applications, sythetic is the way to go.

You try to make it sound like dino is no good. You could run an OM617 on the stuff without an oil related failure until long after every other system on the car is shot.

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2009 VW TDI Jetta Sportwagon 172k miles (rear-ended harder than Elton John on 8/4/13. Total loss)

1991 Volvo 240 142k miles (T-boned by a stop sign runner. Total loss)

I've used lots of Amsoil 15W-40 and Mobil 1 15W-50...do you mean one of those? Or maybe Amsoil 20W-50?

Or do they have a new oil out?

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2009 VW TDI Jetta Sportwagon 172k miles (rear-ended harder than Elton John on 8/4/13. Total loss)

1991 Volvo 240 142k miles (T-boned by a stop sign runner. Total loss)

I am yet to see a good HDEO like Delvac Super or Delo 400 leave any deposits even after extended OCI, synthetics definitely have their attributes but only in extreme conditions which an average person would never face, on top of that the high cost of synthetics makes it a pain for changing oil frequently.

Even UOAs confirm the performance of HDEO and the justification of their use.

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99 Gurkha with OM616 IDI turbo

2015 Gurkha with OM616 DI turbo

2014 Rexton W with OM612 VGT

Oh no! An oil thread!

I use Syn in my gassers, FWIW.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

A senior moment I guess, 15w-40 would be the one.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"