I am sure this has been discussed many time but oils change so this is a moving target. Also, higher mileage engines do tend to like thicker oils. As my car tends to fit into the latter category, I have been looking at thicker options. My first inclination is to just go with Redline 10W40 (97 CSt at 40C, 15.1 CSt at 100C and an HTHS of 4.4 CP) as Redline is typically a bit thicker than most and it is great oil. But I did more digging to see what else might be an option. I have always been skeptical of Amsoil but their 10W40 is actually a bit thicker (103.4 CSt at 40C, 15.7 CSt at 100C and an HTHS of 4.4 CP). I couldn't find any other options that were comparable. However, there are some 15W40 oils out there. The problem is that most of them are for Diesel engines. That doesn't mean they won't work well in a gas engine. Some do. The most commonly used is Shell Rotella but I am not a fan. Redline does have a 15W40 racing oil but it is actually thinner than the 10W40, which is odd. Of the Diesel oils, I ended up coming back to Amsoil again. Their Max Duty 15W40 looks like a good option. (112.4 CSt at 40C, 15.6 CSt at 100C and an HTHS of 4.5 CP) Their Heavy Duty 15W40 is also pretty thick. (112.7 CSt at 40C, 15.5 CSt at 100C and an HTHS of 4.7 CP) This last one should be particularly good at not shearing down to thinner viscosities over time. Any experience with trying these 15W40 diesel oils? Anyone have a UOA on any of these oils?
Amsoil is fantastic oil. Consider this https://www.amsoil.com/p/z-rod-10w-40-synthetic-motor-oil-zrd/ You can find UOA 'son Bitog btw.
M1 0w40 Euro will provide all the protection you need, costs much less, and is readily available. If you race, then I would go RL 10w40 or higher based on temps seen. My $0.02...
I think rotella is the only multifleet synthetic diesel left. I love the stuff. I use it in everything including my racecar. It is also cheaper than gas blend sythetics. It's a winner for me and then I only stock one oil. For coolant is is zerex G05.
If an engine needs "thicker" oil due to being somewhat worn, I think one should look for higher viscosity at 100C and not at the viscosity at 40C. Worn engines typically show lower oil pressure than specified when they are fully warmed-up (when "hot") and, if this is to be improved, then a bit higher upper number could help like 10w-50 or 5W-50. I wouldn't go for higher lower grade number as it may cause poorer oil flow at cold starts (and poorer lubrication), especially in cold weather, and because I don't think it will improve anything in the case of a worn engine.
After thinking about this a little more, I tend to agree with you that the viscosity at 100C is probably more important. Seepage will be highest when the oil is thinnest. However, oil does still seep at room temperature and the car spends more time at room temperature so it does matter. Also, oils with high VI tend to shear down to lower viscosities faster. That actually moved me toward 15W50. You get about the same thickness increase at 100C and 40C. And the VI is about the same at 10W40 so it won't shear down any faster. I think I am down to Redline 10W50 and 15W50. There are some other Motul, Amsoil, Royal Purple and M1 options but I always seem to come back to Redline due to the incredible reputation.
The Z-rod 10W40 is a little too thin but the Z-rod 20W50 was considered. It might be a little too thick at low temps. If they made a 15W50 it probably would have been fantastic.
These oil discussion threads are so much more civil than in the air-cooled Porsche forums where there are a lot of people dying on a lot of different hills
Two things to keep in mind about the damn internet. First, is the person more concerned about proving their choices and opinions are right or are they concerned about finding truth. Second, if the topic is technical, is there an engineer, a good engineer, in the house/discussion? My opinion and direction has changed through this discussion. I am still not 100% sure what I want to do but I am close. But, yeah, civility matters too. I can switch from caring about truth to being defensive pretty easily when the discussion turns rude. But I also know that is a me problem. Fortunately, that hasn't been an issue in this discussion so thanks to all for that.
If considering 15w50, Mobil 1 has a good oil in this viscosity with "healthy" ZDDP of 1300/1200 and it is also designed for flat tappets. I could not find anywhere what ZDDP Castrol oils have. Mobil is about the only oil manufacturer that issues, and regularly updates, their product guides that show the ZDDP content. Latest issue that I have (Oct 2019) is attached as pdf. Image Unavailable, Please Login
If you use the Shell Lubematch it recommends the Shell Helix Ultra 10w-60 https://www.shell.co.uk/motorist/engine-oils/lubematch.html#vanity-aHR0cHM6Ly93d3cuc2hlbGwuY28udWsvbW90b3Jpc3Qvb2lscy1sdWJyaWNhbnRzL2x1YmVtYXRjaC5odG1s=true&iframe=L21vdG9yaXN0L2VuZ2luZS1vaWxzL2x1YmVtYXRjaC9famNyX2NvbnRlbnQvcGFyL2lmcmFtZWRhcHBfY29weS5zdGF0aWMvaWZyYW1lLTAyMTEyMC5odG1sIy9nYi9lbi1nYi9lcXVpcG1lbnQvMzQ4X3RiX2d0Yl8zXzRfMjIxa3dfRmF3RWNXV0N1
Yes but not really for standard engines. The Shell Technical Datasheet for it states: "Developed in association with Ferrari for racing and modified engines.", and "Shell Helix Ultra Racing is designed for modified engines and racing engines using gasoline..."[/QUOTE]
I think you'll find that's just a bit of flattery to make you feel like a racing driver etc. If you check the link you'll see it's for 348s whether used on track or not.
As far as I know, the only car engines for which 10w-60 (Castrol TWS or Edge) was specified by the factory was E30 M3 (and, I believe, some of the later engines in the M-series) and the classic Porsche 911-s (due to engines being air-cooled). When thinking of using higher engine oil grade (higher second number, relevant when the oil temp is at 100C) than the factory specified, the following should be considered (extract from a write-up by an expert from Opie Oils, UK): "The downsides of thicker oil (when not specified) are as follows: - Additional friction, heat and wear. - A reduction of BHP at the wheels - Lower fuel efficiency The thicker viscosity oils lead to a slower oil flow rate, which can lead to several problems. There can be localised high oil pressures in the engine, causing increased wear at certain points as the oilways are not designed to cope with the thicker oil. One of the main functions of the oil is to carry heat away from the engine and that is then cooled by the air flow over the sump – with the thicker oil the flow rate is slower, meaning less heat is taken away and higher oil temperatures occur (that can also lead to people thinking they need thicker oils). In a worst case scenario with thick oils (when not required) is that you will experience air entrainment and cavitation inside the bearings at high RPM." I believe that it is especially important to consider the above quoted advice when one thinks of jumping 2 steps up in the upper viscosity number, like from w-40 to w-60.
Yes, I tend to agree. I am very hesitant to jump to a 60 weight oil. So I am down to Redline 15W50 and 10W50. The 10W50 is only a little thicker at 40C which might help reduce wear at startup relative to the 15W50. But the 15W50 will shear less. The Redline 10W40 is actually thin relative to 10W40 oils circa 1992 so I am very good with jumping to the 50 weight oils. I just need to pick one.
