Hi Dunc, Penrite is a good oil, don't get hung up on Taxi spec, there is no basis to relate to your vehicle unless your engine runs near 24/7 and may include up to 5 hours idling in up to 40deg heat with the aircon on every 24 hours.
The high summer weight relates directly to idling duty once thinned and hot with low RPM engine idling a 60wt will do an OK job of forming enough of a film/barrier over the now slowly reciprocating parts, in that the 60 has its place.
In every other area of duty for an engine 60wt is a poor choice about as poor as using a 20wt for Australian conditions but for different reasons.
The gas oil you are using is a lowly rated oil (CG-4) and was not even a competent oil in relative terms when it was introduced apart from being better than the oil spec it replaced.
With regard to any standard they are a minimum, the 60 oil you are useing needs only to exceed the minimum spec by 0.000001 to exceed the standard (marketing term and who will actually test it in the market place?).
The exceeding a CG rating (marketing term) means nothing although by definition it cannot do any worse of a job than any other CG rated oil. So this oil regardless of additive claims cannot by it's rating protect a gas engine any further than any other CG oil, marketed as a gas oil or not marketed as one!
Today the oils we have are finally becoming good oils, pushed toward us by motoring manufacturers which have been pushed by government which have been pushed by green lobbies.
Todays engines esp the diesels are much dirtier engines internally because they now need to recycle much of their waste product nitrates, sulfates etc back into themselves giving no easy escape for these contaminates like in older engines, now it is the oils job to deal with them no longer mother nature. The modern rated oils have the ability to handle these contaminates in such a way that engine condition is not severely affected, a CG oil cannot protect any engine better than a CH-4 (as a minimum) or a CI-4. Take the opportunity to dump your low spec oil.
There is now an even higher spec oil under review as even the CIs can be improved upon today. I look forward to it's advantages when it is released
Some worthy examples IMO are Dello 400, Rotella, Delvac-1 there are many more, even a penrite CH or CI?, with very few exceptions and almost irrespective of make model etc in real terms if a person is not using a Ch or CI they should be!
The subject is huge and I only know enough to keep myself clear of trouble for the future, consider using a 15w-40 CI-4 for year round protection, honestly CG is for the birds if only for the slow buildup of sludge and contaminates because of a poorer ability to clean, handle and keep contaminates in suspension. Use of low spec oils will see higher mileage engines start to have oil related problems, contaminates instead of staying in suspension will aggregate like plaque in arteries constricting every oil gallery this decreases oil flow everywhere also to the top end valve train causing the oil that makes it to the top to bake before it can drain to safety, this in turn causes more sludge buildup until the engine is completely caked in sludge-it's a given sooner or later with CG oils. run your finger around the inside of the tappet cover at the fill hole.
Just one more thing 60wt oil hot and being forced through a tight journal/bearing gap is one of the direct causes of bearing failure due to the impactand spot related heat it achieves, water is very hard if accelerated, oil when squeezed through a journal at RPM is effectively a solid- Believe it or not!!
It's much much kinder to leave 60s alone and go with a 40 in Australia and a 30 in Europe and colder climates.
Sorry so long, I have a bad habit of trying to save people who use the heavy oils and also the low grade oils. Rightly or wrongly.
I have punished most of my family and friends into changing also. not singling you out, its my problem...really
cheers fnq
cheers fnq