If you have read any of my BITOG posts, you'll have heard me bang on about the problems of high Noack engine oils; particularly in the US.
My basic narrative is that in the right circumstances, hot blow-by gas will, over time, strip out the lightest components from a high Noack oil, route these through the PCV system, through the intake and into the cylinders. This leads to some oil loss and a visibly dirty intake manifold but these aren't the problems you really need to worry about. These heavy hydrocarbons do not burn well and partial combustion can leave behind very heavy, sticky deposits. This stuff can find it's way past the rings and leave deposits in the piston grooves. In extreme situations, this can cause an oil control ring to stick (unlike the top two rings, the OCR is not self-cleaning). Once this happens, your engine's oil consumption is likely skyrocket as oil gets pushed passed the top ring and directly into the cylinder.
The problem of oil front-end strip-out get worse as engines age and wear (more blow-by for a given fill of oil) or, if by virtue of living in a cold climate, you get fuel dilution (re-evaporating gasoline helps oil enter the vapour phase).
I am now wondering if there's another potential impact of high Noack oil in that over time, partially burnt oil can foul Exhaust Gas Recycling (EGR) valves? I've known about EGR for a long time as a means to reduce NOx on diesel engines. However I guess I wasn't so aware how EGR is being applied to gasoline engines as a means to improve fuel economy (by eliminating throttle body losses at load) and controlling knock (as an alternative to over fuelling). If I've understood things properly, EGR seems to feature heavily with the latest generation of TGDI engines.
What I find ironic is that EGR (especially cooled EGR), in lowering the peak combustion temperature, might make the problem of partial combustion of vapourised oil even worse, so you end up with MORE deposits with EGR and more sticky gunk, just waiting to gum up your EGR valve?
This only popped into my head because over here, the news is full of stories of VW fixing their emissions-cheating engines, only to have the fix followed by multiple EGR valve failures (apparently the fix requires the EGR valve to work so much harder).
Anyone else have any thoughts on this??
My basic narrative is that in the right circumstances, hot blow-by gas will, over time, strip out the lightest components from a high Noack oil, route these through the PCV system, through the intake and into the cylinders. This leads to some oil loss and a visibly dirty intake manifold but these aren't the problems you really need to worry about. These heavy hydrocarbons do not burn well and partial combustion can leave behind very heavy, sticky deposits. This stuff can find it's way past the rings and leave deposits in the piston grooves. In extreme situations, this can cause an oil control ring to stick (unlike the top two rings, the OCR is not self-cleaning). Once this happens, your engine's oil consumption is likely skyrocket as oil gets pushed passed the top ring and directly into the cylinder.
The problem of oil front-end strip-out get worse as engines age and wear (more blow-by for a given fill of oil) or, if by virtue of living in a cold climate, you get fuel dilution (re-evaporating gasoline helps oil enter the vapour phase).
I am now wondering if there's another potential impact of high Noack oil in that over time, partially burnt oil can foul Exhaust Gas Recycling (EGR) valves? I've known about EGR for a long time as a means to reduce NOx on diesel engines. However I guess I wasn't so aware how EGR is being applied to gasoline engines as a means to improve fuel economy (by eliminating throttle body losses at load) and controlling knock (as an alternative to over fuelling). If I've understood things properly, EGR seems to feature heavily with the latest generation of TGDI engines.
What I find ironic is that EGR (especially cooled EGR), in lowering the peak combustion temperature, might make the problem of partial combustion of vapourised oil even worse, so you end up with MORE deposits with EGR and more sticky gunk, just waiting to gum up your EGR valve?
This only popped into my head because over here, the news is full of stories of VW fixing their emissions-cheating engines, only to have the fix followed by multiple EGR valve failures (apparently the fix requires the EGR valve to work so much harder).
Anyone else have any thoughts on this??