Originally Posted By: Ducked
The cat stuff doesn't apply to this car and the cold start stuff (which is in any case viscosity-related rather than C-oil specific) doesn't apply in this climate (Taiwan). That leaves
"When you put this extra additive load in a gasoline engine, the effects can be devastating to performance. The detergent will work as it is designed and try to clean the cylinder walls. This can have an adverse effect on the seal between the rings and liner, resulting in lost compression and efficiency."
Could happen with a coked-up engine I suppose, which mine might be. OTOH I'd think it could unstick piston rings and so perhaps
improve performance.
Sounds difficult to predict.
With an engine in good condition (which admittedly mine might NOT be) a dramatic effect on compression seems rather unlikely.
I have, however, read "somewhere" that the over-basing necessary in diesels tends to erode tribofilms in petrol engines, which might lead to higher wear in metal to metal contact areas such as the cam lobes.
I would probably use it (IF I did) blended with CPC SAE 40 which has a base number of around 6, so that would perhaps reduce the effective overbasing of the mixture..
I think you are overthinking it.
Long before manufacturer specific approvals came to light, HDEO was used in many high performance engines across Europe. Although technology has indeed advanced since, the basics pretty much remained the same.
From personal experience, I run
Motorcraft Super Duty SAE 15W-40 CJ-4 in my Pajero with a 6G72 3.0L V6. Other than an EGR system, this vehicle is not equipped with emissions equipment, so that puts us on the same boat. What particularly caught my attention with this oil was no API Service approvals, just Commerical, and a label on the back that read "
Do not use in gasoline engines equipped with catalysts". After looking up the oil a little more in depth, the calcium, phosphorus, zinc content and viscosity at 100 ºC caught my attention. NOACK wasn't much to write home about, but this is a mineral-based oil after all.
For nearly ten years and over 240,000 km, this engine had run on well respected synthetics such as Mobil 1 0W-40 and German Castrol 0W-40 (later Belgian Castrol 0W-40) to name a few, with 5,000 km drain intervals. Things looked relatively clean under the valve covers, although there was a noticeable (not loud but noticeable if you pay attention) tick coming from two of the hydraulic lash adjusters that would quieten down at higher engine speeds. I thought nothing of it, but I did initially limit my drain intervals to 2,500 km after some observations.
Although the oil maintained a light golden color, crud started appearing on the dipstick. This was why I decided it was in my interest to cut the drain intervals by half, and out of curiosity, I cut open the OE Mitsubishi (Toyo Roki) MD352626 oil filter I was using at the time to find even more crud. The oil appeared to be doing some "cleaning", but what it was cleaning was a mystery.
About 7,500 km and 3 oil changes later, one of the lifters quietened right down and now I only had one ticking. After 12,500 km on this oil and 5 oil changes later, the lifter still made some noise, although at this point, slightly raising idle speed made it go away completely. Unfortunately, it didn't have enough time to run its course before a sudden radiator leak on the highway resulted in overheating.
The heads were pulled off, one of the heads was replaced, and all lifters were now replaced in the process since I was at it. The ticking lifter, an intake valve on cylinder 6 (driver's side near the firewall), now a brand new one, did not go away and turned into a major annoyance. A couple of days later, now really annoyed, I decided to pull the rocker arms off the shaft for close inspection. The oil passages on the shaft and rocker were caked in exactly the same type of crud I saw on the dipstick and in the oil filter. The other ticking lifter, that later quietened down, was the exhaust valve on the same cylinder. Although oil could flow through the shaft circuit and the rocker, there were still signs of crud in there that were really hard to clean off, even with the use of solvents. The crud was literally baked on.
The rocker arms and shafts were replaced, and now the engine is as quiet as a church mouse, however it just proved to me that HDEO certainly has its advantages. I will continue running this oil in this application with 2,500 km drain intervals and a new synthetic media filter every 15,000 km at the 6th oil change. Readily available, priced right and works really well.