Hello all, I've been experimenting a little bit with my W140.
When I purchased it, it had Toyota 10W30 in the sump as the PO got it serviced at the local Toyota dealership. It was overfilled about a litre which is a big no-no on these M104s and it even says so on the fill cap.
I sucked a bit out through the dipstick tube and continued but it had a slight lifter tick at hot idle so I dropped it and put in some 15W40.
Lifter tick went but it still had a slight leak, probably from the infamous external head gasket weep.
Since most on the MB forums suggest either a) HDEO/diesel oil, or b) 15W50, I found a 15W50 diesel oil on sale and threw that in plus a new Mann filter.
1100ppm zinc, 11.1 TBN, and a high viscosity of 19.0cSt @100c, perfect.
The engine runs a bit quieter and smoother as expected but to my surprise the engine temp sits around 5c cooler now, with the only variable being the oil - same ambient temps and roads travelled.
Hwy temp would be around 85-87c with both the 10W30 and 15W40 but it now sits around 82c.
Idle temp in traffic has also dropped from around 92c to 89c.
Bear in mind this car has proper oil pressure and temperature gauges that read accurately and in real time, as opposed to the dummy gauges on my newer cars.
I always thought it was common knowledge that thinner oils help keep things cooler, and that has always been my reasoning for using them, especially in newer, leak free engines.
It seems as though people have documented both ways so I wonder if formulation has more of an effect than viscosity?
I'm interested in other people's experiences with this!
When I purchased it, it had Toyota 10W30 in the sump as the PO got it serviced at the local Toyota dealership. It was overfilled about a litre which is a big no-no on these M104s and it even says so on the fill cap.
I sucked a bit out through the dipstick tube and continued but it had a slight lifter tick at hot idle so I dropped it and put in some 15W40.
Lifter tick went but it still had a slight leak, probably from the infamous external head gasket weep.
Since most on the MB forums suggest either a) HDEO/diesel oil, or b) 15W50, I found a 15W50 diesel oil on sale and threw that in plus a new Mann filter.
1100ppm zinc, 11.1 TBN, and a high viscosity of 19.0cSt @100c, perfect.
HPR DIESEL 15 15W-50 (Semi Syn.) | Penrite Oil
HPR Diesel 15 is a premium high performance semi synthetic SAE 15W-50, non-friction modified engine oil. It features a DOUBLE LAYER of engine wear protection with FULL ZINC and Penrites advanced EXTRA TEN technology. It contains a combination of high technology additives, including increased...
www.penriteoil.com.au
The engine runs a bit quieter and smoother as expected but to my surprise the engine temp sits around 5c cooler now, with the only variable being the oil - same ambient temps and roads travelled.
Hwy temp would be around 85-87c with both the 10W30 and 15W40 but it now sits around 82c.
Idle temp in traffic has also dropped from around 92c to 89c.
Bear in mind this car has proper oil pressure and temperature gauges that read accurately and in real time, as opposed to the dummy gauges on my newer cars.
I always thought it was common knowledge that thinner oils help keep things cooler, and that has always been my reasoning for using them, especially in newer, leak free engines.
It seems as though people have documented both ways so I wonder if formulation has more of an effect than viscosity?
I'm interested in other people's experiences with this!