Which engine oil for a quick top-up.

[Iyarno]

Wow, thanks everyone for you time. More info than I could ever have dreamed of, especially as I thought I'd be referred to an existing thread.

I'll be taking the +2 for a run at the weekend, and I'll check the oil level again after a short while of standing. I suspect it is low however, as I get a small amount dripping after every run. As I mentioned, the car has only been in my possession for a month or so, and I was handed minimal info about its history. I do know the engine has been rebuilt, and my 'best guess' is that was done within the last 10 years or so. As for the oil that's in the engine at the moment, it's anyones guess.

I have got some 20W/50 oil and a new filter is on the way. I don't about it's ZDDP content which is all new to me. For now I'm going to avoid throwing money at it until I can get it to a specialist who can advise better on what's been done and what hasn't. I've posted some pictures on Flickr of my Lotus in question. Perhaps someone on here recognises it and can tell me more about its history!

http://www.flickr.com/photos/ianstuartweir/sets/72157626030808731/

Ian
__________
68' Elan +2
83' Golf Mk1
Campervan wanted

[Esprit2]

Penrite has a good reputation and does make high ZDDP oils, however, not all their oils are high ZDDP. Refer to the Penrite spec sheet that was posted in an earlier message for ZDDP levels by grade.

Note that you're not primarily concerned about zinc. It's phosphorus that is required, and it comes in the form of the compound zinc dialkyldithiophosphate (ZDDP), which contains both zinc and phosphorus. The long chemical name starts with "zinc", so everyone focuses on zinc, but that's not correct. If you read a data sheet that lists both, pay attention to the phosphorus first. If it just refers to zinc levels, then you can't be certain if they're talking about zinc itself or the total compound ZDDP, but neither is the phosphorus value you seek. You will be in the phosphorus ball park if you take a reference to zinc and deduct 100 from the value. 1300 ppm zinc via ZDDP will result in about 1200 ppm phosphorus. Crude, but close.

Target 1000 ppm phosphorus as a minimum. Not a comfort level, just a minimum. 1200-1300 ppm phosphorus is a good place to be with our engines, but...

In addition to reduced Zn and P levels, many modern SM oils with "adequate" ZDDP also use newer Calcium-based detergents, which SAE publications have documented as causing more wear than the detergents previously used in the older API SH/SJ oils. Depending on how much detergent an oil has, and which detergents are used, optimal phosphorus levels for vintage flat-tappet cam engines can range from 1200 to 1500 ppm. If you use an SM oil, shoot higher.

Finally, just to confuse you more, there's such a thing as too much ZDDP since too much can also cause corrosion problems for the engine?s metals. It has been shown that at around 1500ppm, zinc begins to erode the boundaries surrounding the metal?s microscopic grains. In some situations, the benefits of more phosphorus out-weigh the risks associated with more zinc; but if you?re not qualified to make that call, be conservative about throwing more ZDDP additive into a high-ZDDP oil just because, ?more is better?. Sometimes it?s not.

For a planned track day, the anti-wear benefits of 1700-1800 ppm phosphorus might outweigh the short-term exposure to the risks of high-zinc corrosion; but for full time street use, it might be better to drop the level down to the 1200-1300 range. The risk of zinc corrosion is one of the main reasons why racing oils are not recommended for full time street use.

*~*~*
The trouble with additives like ZDDPlus is that if you don't know the ZDDP level of the oil you're starting with, you don't know how much additive to pour in to achive your target level. Hmmm... I don't recall for sure, but it seems to me that ZDDPlus doesn't even state it's ZDDP level on the label.

Off-the-shelf additives are not the best solution. ZDDP works optimally in the presence of other additives like molybdenum disulfide (Moly) and sulfur in specific, delicately balanced proportions... it's a package deal. Simply pouring in a bottle of ZDDP without the other complimentary elements doesn?t yield the ?more is better? result one might expect.

Just grabbing any old oil and pouring in a bottle of ZDDPlus shouldn't give you a great feeling of confidence. It's best to shop for a properly blended oil that you know comes with an appropriate ZDDP level. Finding one is where it gets tricky.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)