Engine Oil Yet Again

[tigerdog]

Anyone here tried Liquimoly's new 5W-50 full synthetic? Sounds like a perfect compromise between full flow at low temps and good protection at extremes.

[FunElan]

You live in San Diego...there are no extremes

I've used 10w-30 and 5w-40 and prefer the "regularity" on the oil pressure gauge with the 10w-30.

[tigerdog]

I corresponded with Liqui-Moly and it seems they do not recommend the 5W-50 for the Elan. Next thought is to go with Mobil 1 5W-50. Both of them are still thinner than 10W-30 when cold but thicker than the 5W-40 I'm using now (at least according to the technical spec sheets.) So the oil change project will happen as soon as it stops raining here. I really miss having a garage.

[chrism]

I just tried a 50/50 mix of 10W-40 semi synth and 5W-30 synth and the oil press seems 'just right', no start-up rattle etc.

I'm working along the lines that perhaps you get 'the best of everything' doing it this way?

edit ps: does that mean it's 7.5W-35?

[dapinky]

edit ps: does that mean it's 7.5W-35?

Yes, it does!

It is a linear scale and it is no problem mixing different viscosities to get the numbers required.

Obviously, it makes sense to mix oils of similarities if possible (ie, synth with synth etc) and ensure that both (all?) parts of the mix meet the required standard, and (not applicable to our engines) have the correct additives in them.

It can be hard to find 5W40 in a 'good' synthetic make, but mixing 5w30 with 5w60 in a 60:40 ratio works out close enough.

[chrism]

...had to work it out - it gives 5W-42 - but in all seriousness it means we can hone in and provide for the peculiarity of our own engine's state of wear.

eg I felt 10W-40 Magnatec eliminated start-up rattle yet the gauge was rather noticeably high whereas 5W-30 Mannol (btw both A3/B4 - watch out cos some Magnatech isn't..) puts the gauge 'right' but throws a few seconds of rattle.

DaPink the nice thing about your 5W-42 solution is that it 'covers' those essentials but with a fully synth bonus

[dapinky]

Chris,
I was never happy with 5w30 in my car since I had it stuck in traffic on a hot Summers day many years ago. I was on the M5 so couldn't really pull in to allow it to cool down properly and the temp gauge was high (this was before I fitted the fan override switch), whilst the Oil Pressure was low. I had a choice between having the heater on full blast or cooking the engine (or seizing it up!), so I had a very uncomfortable hour or so until I could get moving, and then drove really steady to get the temp down without straining the engine....

.... not a fun drive, TBH.

After that I started using thicker oil, and ended up with 10w60 (Fuchs Titan) synthetic.

It seemed good, so I kept it for a few years, then decided that the oil pressure was actually higher than I would like (on the gauge, so don't know what it really was running at) when cold. I thought that the high pressure on a cold engine could cause issues with the rubber seals until they warmed up and became a bit more pliant, so started looking for a decent alternative.

That's when I found out that it is okay to mix viscosities to suit needs, so started to play around a bit using up all those 'old' bottles of oil with a litre or so in each.

I now use a 'base' of Fuchs Titan Supersyn 5w40, with about half to a litre of 10w60. With the mileage on my car (140K) it puts the gauge where I want it to be under general driving conditions, but as I no longer track the car it is probably not worthwhile to go to as much trouble as I do, and I could just use 5w40 on its own - but I like it a tad thicker.

I'm sure it is a little bit psychological, but it keeps me happy!!!!

[Tuga2112]

what gets me about the topic of oil thickness is the fact that no one actually knows what is the gauge meant to tell us.

my understanding (and correct me if im wrong) the general consensus is that the gauge is just an overal indication that theres some pressure in the engine. and i never came across someone saying "from this point up to that point your good" the general rule is. "if its reading zero or maximum you have a problem" this feels too binary of a guideline to justify the gauge.

ive been running 5-30 for years now and i get readings outside the zero and max. but i have no idea if i should switch or not.

[chrism]

HI Tuga. 2.5bar is ~36lb/sqin, 3 is ~44, and 5 is ~73 and I seem to remember a fig of 44lb/sqin from BMC-ish Smiths oil-pressure days on tickover.

This pic is like my typical warm idle reading. Start-up can be a bit above 6bar with thicker oil - so anything around the middle of the dial resonates with my past experience and also fulfils your 'outside zero and max' expectation too.

It's a shame the temp dial is a 'box of frogs' but as soon as we use EScan to verify that the miniscule movement represents ~82C plus then all is well.

(Incidentally I know we seem to have ES acquisition probs with the later win versions, but does your n/a ecu respond to ES in the usual way - or it it only the turbo'd versions?)

[Tuga2112]

afraid i cant help.

"my" cables were borrowed from a NELOC member. never plugged to NA cus there was no need.

hoping to find Geoff in this island sometime and willing to produce/sell me a set. i think its about time i get them

[dapinky]

The ECU for a NA car is substantially different to that in the Turbo models (because it doesn't need to monitor anything like the number of sensors etc), and Elanscan won't connect to it (electronically!).

[tigerdog]

Yes, it does!

The other thing to note is that there are notable differences in oil viscosity with the same nominal base weight (e.g., 5W, 10W) A little digging will find the technical spec sheets from the refiner. Look for numbers like this: Kinematic Viscosity at 40 °C 115,0 mm²/s (Liqui-moly 5w-50) or Kinematic Viscosity @ 40 C, mm2/s, 104.3 (mobil 1 5w-50). Typically they'll also spec viscosity at 100 C, so you can get a sense of how much the oil thins out with heat. There's another useful ASTM number, Viscosity Index ASTM D2270, calculated from the kinematic viscosity numbers. From the ASTM web site:

4.1 The viscosity index is a widely used and accepted measure of the variation in kinematic viscosity due to changes in the temperature of a petroleum product between 40 °C and 100 °C.
4.2 A higher viscosity index indicates a smaller decrease in kinematic viscosity with increasing temperature of the lubricant.

Looking at the oils I'm considering, it looks like Mobil 1 5W-50 has a higher 40 C viscosity than the 5W-40 Liqui-Moly I'm currently using. Also, it has a higher viscosity index, meaning it will thin less with heat. What this really proves is that if you have time, you can really learn a lot by reading things on well-vetted Internet sites It may simply be worth reading the gory details of the technical specs to find an oil that brings what you want.