Most 5w-40 I’ve seen is synthetic. Are there any concerns switching to synthetic for an engine that has been running conventional for 20 plus years and several hundred thousand miles? I remember years ago people saying it would loosen sludge and cause leaks. I’d like to use 5w-40 but my engine is relatively leak free and I’d like to keep it that way. At the same time, mine has 15w-40 conventional and seemed to work fine so far this winter, except for -20 when the block heater wasn’t working.
anymore no as synthetic oils are designed to meet same standards but with longer life span before oxidation and such and most oils they call synthetic here in USA is actuall group II / III hydrocracked crude oil aka dino oil not a real synthetic oil aka group IV / V
https://www.pca.org/news/2015-11-02/synthetic-word-relates-motor-oil companies cheat and say II/III are full synthetic when they are not they only require a small amount of synthetic additive to be called full synthetic here.
Group III — Wax isomerized or hydrocracked crude oil refining process. Group III base stocks are considered synthetic because their molecular structures are altered through an intended chemical reaction. Very low wax and aromatic content. Used in the
majority of synthetic motor oils.
which is not really synthetic oil its a cheat oil manufacturers use to lie to you about it being synthetic
This is why alot of GDI engine owners are having major issues with theyre engines due to the lie about being synthetic when it is not a GDI engine is super finicky about oil and only a true synthetic will have a good enough NOACK volatility number
https://en.wikipedia.org/wiki/Noack_volatility_test
Our engines also are in this boat as we need a low NOACK volatility to keep our oil in the motor when towing we have piston squirters shooting oil on bottom of a piston at over 500f this will cause fast evaporation of oil which rotella is horrible about now also when the oil flashes off in this way it causes the oil to thicken and get sticky this can land our engines with sticking rings and sticking CDR valves which will literally blow every seal / gasket out of our motors making them puke oil constantly and also major sludge formation issues.
I have been testing other oils and have come across one i really like but suddenly it got hard to get
http://english.sinolube.com/content/details15_570.html
https://www.walmart.com/ip/15W40-Fu...gine-Oil-5-Gallon-Pail-18L-4-75-GAL/848072546 this oil has been doing awesome for me for past year+ we are talking much better than any other oil for the price and my oil analysis reports confirm this oil is doing very well even with 10,000 mile oil changer interval with motorcraft FL1995 oil filter.