Synthetic or not?? What should I use?

[Angry Tape]

Alright...the first oil change on the TD is coming up (mobil 10W-40 for break in period).  THis is usually the time I switch to synthetic.  However...most synthetics are not approved for diesels.  So heres my predicament.  Delvac 1 synthetic only comes in 5W-40 which seems much to thin to me.  Regular Delvac comes in 15W-40 (which is what I want to use) but its not synthetic.  The Turbo charger is telling me I need to use synthetic but the motor is telling me dont dare but 5 weight oil in me.  SO what do I do?  Is it okay Not to use synthetic and just use a good quality diesel oil or should I keep looking for a synthetic diesel oil with 15W-40?  ANyone know of one?

-CHris

[fspGTD]

5W40 (synthetic) seemed to be a nice upgrade over 15W40, based on my experience.  It's the same weight when hot, but doesn't thicken as much when cold.  What I found was more available power, torque particularly in the winter when the motor was cold, and better starting, running, and fuel economy, also particularly noticeable on a cold motor or in cold running / cold weather.  It starts easier, turns over quicker, runs smoother, more power when cold....

Keep in mind back in '83 when VW developed the motor and specified what oil to use, they didn't have synthetic 5W40 available as an option.  IE: the synthetic technology just wasn't available in the market then like it is now.

Now that said, maybe I'm not the best one to listen to on this topic at this point in time, as I was having some potential low-oil pressure problems (but I believe they were because of my removing the vacuum pump and replacing it with a block-off plate, which is for some reason maybe sapping more than it's fair share of oil flow.)

Anyway, rest assured I have done oil analysis with Mobil Delvac 1 at 10K mile change intervals (filters changed at 5k) and all the analysis came out OK.  That was years ago, back when I daily drove my 1.6lTD (before I converted it's primary use into a dedicated autocrosser like it is now.)

[RAMMSTEIN]

Amsoil has some 15W40 and 10W40 full synthetic diesel rated oils.

That would be best.

You also could put 15W50 Mobil 1 which has API CF ratings, with are enough for a TD.

I'm sure 5W40 is alright for your engine. As long as the oil you use is 40 weight and made for diesel engines, you'll be alright IMO. :wink:

[fspGTD]

Also, consider that on VW's newest turbo-diesels, they have changed their oil specifications to specifically, a synthetic 5W40 oil (CG-4, IIRC.)  IMO, the reason why VW didn't specify this oil on their earlier IDI-TD motors was availability.  If there was a 5W40 synthetic diesel oil available in the mid-80's, I think VW would have recommended it for their IDI-TDs.

IMO, the need is particularly acute on these early IDI-TD motors without watercooling in their turbochargers (which the newer TDIs have incorporated.)

[farkman]

Chris

The thickest 15W-40 dino oil I've found is Shell Rotella. It has a viscosity of 15.7 cSt. This number is based on the actual oil viscosity at 100 degrees Celsius. D1 (now Mobil Truck & SUV) is thinner at 14.8 cSt but it does have a higher total base number (TBN) to counter the effect of the oil turning acidic. D1300 is almost as thick at the Rotella at 15.6 cSt and has the same TBN as the D1. Plus it's pretty cheap too . Really though, you'll be fine with any good oil, dino or synthetic. But if you drive the car hard, want that extra bit of fuel economy or will encounter really cold temperatures go with the synthetic. I have D1 in my car right now and it has performed flawlessly, but will be changing to Amsoil 5W-30 heavy duty diesel in the fall.

Peter

[QuickTD]

IMO, the need is particularly acute on these early IDI-TD motors without watercooling in their turbochargers (which the newer TDIs have incorporated.)

As of the 2004 PD TDI, VW has not used a water cooled turbocharger on a diesel. The 1.8T gassers all use water cooling. VW has apparently reasoned that the diesels, due to their inherently lower EGT's, do not require it.

I would still recommend a synthetic 5W40 diesel oil, especially for the winter months. Cranking speed is very noticably improved. Contrary to popular belief, I find my oil consumption is considerably lower with synthetics. The only downside to synthetics is cost. There are some less expensive oils, petro canada duron synthetic is one. While it isn't a true PAO synthetic the performance is very similar and the cost is reasonable at ~$4.70CDN per litre. Extend the change intervals a bit and it becomes no more expensive than conventional oil.

[Rat407]

Amsoil also has a 20w-50 that is diesel rated.

 http://intershop.amsoil.com/cgi-bin/Amsoil.storefront/4110d7990497eeec271bd1f0e3f0073d/Catalog/1472

[Angry Tape]

Im just worried that 5W-40 is going to make my already touchy oil pressure problem even worse.  With 10W-40 I run about 11-12psi at idle.  Im worried this number will fall if I go 5W-40....which is why I wanted to run a 15W-40 or 50.  What do you guys think?

Thanks for the input thus far

-Chris

[farkman]

Chris

What 10W-40 oil are you using? The only oil I found on the Mobil website is thee new Drive Clean oils.

Peter

[Angry Tape]

yeah...just genaric mobil 10W-40.  Only have it in for 500 miles for break in.

[farkman]

Chris

Is that oil even diesel rated? The specs on that oil show that it's a relatively thin 40 weight oil at both 40 and 100 degrees C. I would just try the Delvac 1300 since it isn't that expensive and it's considerably thicker than the 10W-40. By the way, do you know what the oil pressure should be at hot idle? 15 psi doesn't sound too bad at hot idle. What's your oil pressure above 1500 or 2000 rpm? Since you've only gone 500 miles on the 10W-40 stick with a dino oil until you've done about 5000 miles.

Peter

[Angry Tape]

oil pressure is up around 30psi at 2000rpm.  I still feel that is low on a freshly rebuilt motor.  My dads plain diesel with 260k on the clock had 28psi at idle warmed up.  The pressure switch knocks the low pressure light on at 27psi.  Im hoping maybe my oil pump is crap.  I have a new german pump coming from germanautoparts.com as we speak.  Ill throw the pump in and fill her up with Delvac and see how she does.

Thanks for all the reply's guys.  Other than the oil pressure the Rabbit is an absolute blast to drive.  I let one of my friends scott drive her and he couldnt believe it.  Said it felt like an 8v GTI