didnt realize there was that much difference at idle in a diesel, but, gasoline engines are also much more precise when it comes to fuel. if its too lean by even 2 points in a certain RPM range, there's detonation.
Fine (and welcome to the board, BTW), but you're still not addressing my point. Even if what you're proposing is true, why do identical engines in Europe recommend thicker oils than the same engines here? Are engines in Europe somehow magically immune to the "lean load idling" you're talking about? Obviously, there is a difference in philosophy, policy, or opinion that is fueling the difference, not manufacturers' engineering requirements. Which is better, lighter or thicker? I don't know, but the manufacturers must have an opinion on the subject and I don't think you can discern that opinion based solely on what is recommended for cars in the US or what is recommended for cars in Europe.quote:
Originally posted by Durrr:
well, if a car is idling, its using a higher Air to fuel ratio by default, and that, as a result results in more carbon due to the higher oxygen content of the combustion. If you put a load onto the engine it wasnt designed for at that RPM, then it adds a bit more air, and the same amount of fuel, resulting in even more undesirable emissions. Light oils allow it to idle w/ considerably less load.quote:
Originally posted by 427Z06:
I'm not quite sure I understand what you mean by "lean load idling". My experience with that term is when it's associated with diesel engines.quote:
Originally posted by Durrr:
First time posting, but, ever think this is the way that the car companies here in the US appease the EPA and their fuel standards? If your engine requires more torque to idle, your hydrocarbons instantly go up due to lean load idling..
If you simply mean the additional load put on a engine due to minutely thicker oil, I believe tests in a scientific setting are showing about a .1 MPG improvement in fuel economy with these "new" oils. How much more emissions could be contributed due to this additional load? .5%?
Just to clarify, my point is that thicker oils in most engines are OK, and likely better long-term for engine wear.quote:
Originally posted by nortones2:
Kev99sl: agrred that vehicles have a mix of sppeds and loads, but the mfr doesn't know whether the driver is the blue rinse type, or pushy rep. who lives on the autobahn or mway. The vehicle has to cater for both. As for "heavy" oils, the fuel consumption of small engined cars seems to be perfectly OK on the diet provided by 10w-40 etc. However, if your vehicle population includes a large proprtion of 4x4's with a large frontal area and 2 ton weight, then somehow there has to be a compensatory reduction. Albeit minute, when you consider returns like 10-15mpg from gasoline engined SUV's. What improvement in mpg will a 20 weight oil give? Raise the mpg to a range 11- 16.5mpg? Just curious.