Engine oil 成分

Simon

The lawyer bit relates to a court case involving Castrol. They changed their formula from a group IV base stock to using group III. Mobil took them to court and unfortunately Castrol won. As a result a lot of companies changed their formula as well. So most of the so-called synthetics on the market today are based on inferior group III base stock. One major short coming of group III oils are their change in viscosity over time. This means for e.g. that a 40 weight oil will turn into a 20 weight oil. This is because group III oil doesn't have good shear resistance - meaning that the molecules get chopped up reducing the rated viscosity of the oil. Group V oils have excellent shear properties and maintain there viscosity for life of the oil. In addition group V oil provides excellent startup protection, lubricity and fuel efficiency. This is due to their attraction to metal surfaces. They are also excellent at preventing sludge and varnishing. Group IV oils are poor in this area and are often mixed with 10/20% group V base stock. Group IV and V oils are thermally more stable with good low and high temperature performance.

I certainly wouldn’t use anything less than a group IV oil, especially if your engine is mainly used on the track.

coupeelvin

IMO, 0W-40 doesn't perform as good as 5W40 in terms of durability. So, you'll need to change at shorter mileage. But careful of oil consumption too.

romeochris

My K20A specified to use 5W-40, can I use Mobil syn 0W-40? Or shall I use Castrol EDGE Syn 5W-40?

古惑強

One possibility is that when the engine manufacturer (either Rover or  Toyota), , their warranty package would have specified the recommended oil spec.,  hence nobody in Lotus wants to change it,as it would involve extensive re-testing and re-validation +$$$$$$!

Simon

Lotus has specified the use of 5W40 synthetic oil. They have stated that 0W40 is not the proper oil to use, while admitting that the oil did not need to be drained and refilled in an engine that received 0w40 Mobil oil by mistake - but they continued to indicate that it should not be used regularly.
唔知何解.

Simon

copied from
http://www.lotustalk.com/forums/f312/engine-oil-8142/

Simon

Over on an SVT Cobra website I have followed for the past 6 years, we had a ?petrochemical engineer go thru a multi page evaluation of oil. Mobil1 used to be a type iv lube, it is know a type III lube, but is still probably the best one out there. Here is my list I saved and rational for use

Group V: only needed for true racing
Redline
Motul

Group IV: Best for long drain intervals, towing, high temps, hard driving ie track days
Mobil1 Tri-synthetic (discontinued)
Amsoil
Mobil 1 Super-syn is closer to a group III lube but have multiple patents on a new molelecule that should keep it as a top tier product

Group III: cheap synoils. Buy only if the price is right as they are inferior to Group IV products which typically cost little more
Castrol Syntec
Valvoline Synpower
Pennzoil Synthetic
Havoline Synthetic, Exxon synthetic etc (some of the best priced synthetics around)

Group II: Highly refined mineral oils
Valvoline All climate
Pennzoil PZL turbo (Very good product except below 15 degrees)
Royal purple.

In conclusion, all these oils will do the job, choose your product based on need. Notice syn blends never mentioned, a 1% blend is still a blend. Ripoff
Group III's are fine but for typically no additional cost over Castrol, Valvoline, or Pennzoil you can use Mobil1 and have just about the best readily available oil around without kicking out $7-10 dollars per qt although these numbers may change due to increased fuel costs.
PS that article is MIA as this was created in 9/2002 and modified in 2003 when Mobil1 supersyn was released. And no, he doesn't work for Mobil or Exxon!!