My car is a 2003 Renualt Megane 1.9dci turbo diesel. I have posted some 1500+ messages about this car on an owners club forum so like to think I know one or two things about it. I've had the car since 2005 and it does mainly short (1-2 mile) stop start driving. It has around 45k miles on the clock.
The main point I would like to make is that these cars are notorious for blowing turbos (Garretts) and are highly reliant on good oil. I change the oil and filter every 3000 miles or 6 months using Mobil 1 0w40 fully synthetic. It is always very black. The car is in good mechanical order so far - I have been lucky - see below.
Now for some bad news. A while back (2006-2008) I had a period of poor health and was unable to change the oil for this 2 year period. It never needed topping up until this time and I have no idea what oil was in from the purchase date until that time (around 3 years). Probably some dealership generic and not the quality M1 stuff I used now. After I performed the change, the engine started using maybe 1 litre per 1000 miles. There is a small leak (it doesn't drip but streaks) from the turbo charged air side. I have removed the intercooler and all associated ducting and found only a light film of grease inside. It doesn't look like the turbo seals have failed. The car smokes a fair bit from cold and under heavy acceleration. I suspect that this is where the oil is being lost. It does easily pass the emission part of the UK annual test (MOT) when fully warmed up. The measured reading was 0.62 1/m with a limit of 1.5 1/m.
After starting it on M1 oil, I experienced two odd situations on long drives (200+ miles) that I have put down to the cleaning of the M1 oil. Around 50 miles into a drive towing a caravan (US: trailer), with the turbo under constant load, I coasted down an incline to a junction. When I tried to pull away again, the engine would not rev. Contrary to just about all conventional thinking, I floored the pedal in neutral and the revs increased slowly - with no turbo sound. When it hit around 3000rpm the turbo burst into life and the problem went away. As I returned from the trip the next day (having covered 400 miles) I checked the oil level and found half had gone (around 2 litres). I immediately changed it and this has not occured since (5000 miles). I also found that the crankcase breather oil return tube was completely blocked with wax. This problem has been solved. The engine gets plenty of maintenance now including the EGR valve! The EGR system on these cars is plain weird.
Anyhow, after all of that (are you still awake at the back?!) should I risk some Castrol GTX mineral and Auto-RX for 3000 miles or not?
Grateful for any thoughts. If I get favourable results, I will recommend the product to a large number of UK drivers.
Yes, there's no risk with a conventional oil for the duration you're going to use it. Find a conventional diesel oil in the 40 grade flavor if you feel more confident with it.
Interesting issue with the turbo not kicking in at the prescribed time. I would suspect that there was some waste gate/actuator issue involved ..turning the turbine into an exhaust blockade with no benefits for being there.
Any coke formations in the pistons/turbo should be removed and all other paths of forced circulation will be tiddied up nicely. Those areas will see the most heat, even under your short trip scenario. Other areas will clean up as the environment allows Auto-Rx opportunistic leverage. Lots of oil flow at temp? Faster cleaning of that splash/incidental contact area. Variable flow at temp? Variable cleaning of that splash/incidental contact area.
Yes, there's no risk with a conventional oil for the duration you're going to use it. Find a conventional diesel oil in the 40 grade flavor if you feel more confident with it.
Interesting issue with the turbo not kicking in at the prescribed time. I would suspect that there was some waste gate/actuator issue involved ..turning the turbine into an exhaust blockade with no benefits for being there.
Any coke formations in the pistons/turbo should be removed and all other paths of forced circulation will be tiddied up nicely. Those areas will see the most heat, even under your short trip scenario.
geeaea,
Thanks for your reply. Castrol do a 10w40 mineral oil that is B3 specified (minimum requirement for this vehicle) for half the price of the Mobil 1. I think it will suffice if carbon buildup on the turbo bearings will be removed.
The mystery of the turbo was never fully explained. Your theory makes sense - although typically of a French car and probable needless complexity, the turbo has no wastegate - it is variable vane on the turbine side with a vacuum/plenum actuator controlled by a solenoid. The engine managment computer (ECH) controls this solenoid by measuring the boost pressure. It is just about possible to reach in with a hand to check that the acuator is free to move. This is now part of my weekly checklist! There were no OBDII codes flagged after the incident - I checked.
My theory was that due to the negligent oil change interval and subsequent high detergent oil, some debris temporarily blocked the turbo oil supply - the rising engine revs then increased the oil pressure and the debris was released.
If you are confident that Auto-RX cleans as gradually as is claimed (and after several doses of the Mobil 1 anyhow), I'll go buy some. It's priced in the UK at £17 for a 12 fluid ounce bottle - quite a markup on your $20. Such is life!
Yes, getting anything across the pond is expensive ..for both of us. I'd love some Avon Rangemaster "tyres", but no importer ..so it's $$$$ to get them here. I owned a Peugeot 504 wagon ..pre turbo, but I see the French haven't changed their cultural propensities in automotive design. I "loved" the car ..and had an outstanding relationship with the dealer. They loved me too. lol
Typical decoking debris can be found in the filter. It forms a fine grit due to the filter media causing it to collect in the pleats. You can crumble it to as fine a particle as you please. That's how it arrives there.
-- Edited by geeaea on Saturday 1st of January 2011 03:37:30 AM
