Rudy602

I usually use the synthetic 5/30 for the winter and 5/40 for summer but I haven't seen the 5/40 lately but they do have the 0/40. Any thoughts on whether it's a good option for a first or second generation RX - or not?

Baetke

Keep in mind that on a VVT engine the oil serves not only as a lubricant for the engine but also as hydraulic fluid for the cam actuators so the viscosity the manufacturer recommends should be followed so as not to interfere with the response times of the VVT.

fastnoypi

haven't used it but the cold weight of zero would be good for the winter if you are exposed for long periods of below zero temps. You won't find any benefit of the 0w40 compared to the 5w40 Otherwise, i find it too costly an oil for benefit in a car that consumes a bit of oil.

Rudy602

Thanks for the replies. I hadn't considered an effect on the VVT. Would this marginal difference in viscosity have a negative effect? I've used the 5/40 and never noticed any issues. We averaged 12 degrees for the month of Feb. here. I've always considered oil quality to be cheap insurance and money well spent. I don't baby my vehicles but have never had a motor related problem despite the high mileage I rack up on them. BTW, the 5/40 and the 0/40 meet the European standards for Porsche, Mercedes, BMW, etc. All thoughts are appreciated.

Baetke

If anything, I would expect the effect on VVT to be marginal due to a change is actuator response time. Perhaps a small change in power on acceleration and increased emissions on deceleration but I couldn't say if it would be noticable to the driver. Keep in mind that the manufacturers design and test these things to temperature extremes so sticking to the recommendations in the owners manual will not cause any problems.

salimshah

My 2c ...
Keep the spread as narrow as possible based on your environment.

Salim

matts6887

Im sorta wondering the same thing but on a slightly different path. What general good quality oil would peep out there on these forums suggest for a desert climate such as that here in AZ? I mean is there one better brand than another for hot climates or is something like valvoline or penzoil good for a high mileage vehicle like my 99 rx300?

Rudy602

I don't think the brand is as important as the viscosity. I also think that synthetic oil is less prone to sludge build up. Castrol has a "high mileage" oil that has an additive package and Valvoline and others probably do also. Lucas makes a synthetic [and regular] oil "stabilizer" that is supposed to provide additional protection. I'm not a big fan of additives or miracle cures but Lucas makes quality products and I've had good luck with Castrol for over 30 years - and I have no connection to either company except as a customer. My only problem with Castrol is that it is made by BP. Nothing is better for any vehicle than changing the oil when it's time. Arizona likely has a smaller temperature swing than NH where we see temps down to -30 in winter and 100+ in the summer.

matts6887

So; with that in mind Rudy; I wonder if it would be a good idea after each oil change to add a oil stabilizer like something from Lucas to somewhat give the oil more "protection"?

Rudy602

For a high mileage engine in the Arizona heat, I think it would help. Maybe replace one quart or even half a quart with the synthetic stabilizer at each change. Be sure it is the synthetic as the regular stuff is too thick for these motors.

fastnoypi

The thickness is the tested viscosity grade regardless of synthetic or conventional.
The big difference is the additive packs that may prevent quick sheer down, similar to a lower viscosity grade.
If the oil brand selected is known to sheer down, a stabilizer may help.

IMO, i would send a sample of my used oil for analysis and get feedback if my choice of oil is sound for the oil change interval. If it isn't doing its job, i would reconsider the brand and/or step up to a 40 weight. And send for analysis again to note any improvement in protection.

matts6887

Well; I think for my first official oil change on my current 99 300; I will probably go to a shop to have it done as I dont have the facilities to do oil changes plus the hoa frowns on people doing that out in the visitor parking area here. So with that in mind; After I get the oil change done I will probably get a synthetic stabilizer and dump it in the oil fill hole just for hopefully some added protection against sludge.

hypervish

Stay away from snake oil (i.e.additives).

Just change your oil regularly, you'll be fine.

matts6887

whats wrong with adding a oil stabilizer to it after a oil change to try and prevent oil sludge? I mean; if its one thing i dont want to happen its getting oil sludge because that will create one giant nightmare to try and fix. Because then ya gotta tear everything apart and blast everything completely clean, drain any old oil and try and start over again which is the last thing I need to deal with.

hypervish

Google is your friend.