View Full Version : Motor Oil

02-07-2003, 11:20 PM
Aloha All,

I started out researching various types of motor oil to see what might be best for my older LBCs, a '54 MG and a '58 TR3. The car maintenance manuals generally specify a 30 weight motor oil.

Modern engines have closer machined tolerences and most manufacturers specify 10W30 motor oil.
This is oil that is a 10 weight oil that will not thin more than a 30 weight oil when hot. This is acheived by adding polymers to a light base (10W), which prevents the oil from thinning as much when it warms up. At cold temperatures the polymers are coiled up to allow the oil to flow as the low number indicates. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. Generally, the greater the viscosity span, the more polymer additives in the oil. These polymers break down over time resulting in engine deposits, viscosity and thermall breakdown.

The purpose of my long discussion was to say that multi viscosity oils are great for modern cars, but may not be best for older LBCs. My conclusion is that a single weight high detergent oil may be a better choice. I'm inclined to use an SAE 30HD motor oil. The temperature range in Hawaii is small, about 60 deg F minimum over night low in winter to 95 deg F maximum day time high in summer.

I would like your opinions on a motor oil for my cars. These are drivers, I use one to comute to work every day.

Safety Fast,

John Turney
02-08-2003, 02:11 AM
If it wern't for rust, Hawaii is such a perfect place for a LBC. When I was stationed at Pearl Harbor, I had a TR4A. Brings back fond memories images/icons/grin.gif

Anyway, to oil. My impressions are:

- Oil manufacturers don't put as much effort into additives for single weight oils as they do multi-weight.

- The tolerances on a rebuilt engine should be about the same as on a new engine.

- The tolerances on an older non-rebuilt engine would be wider, requiring a more viscous oil.

- The narrower the viscosity range in percentage, the better. ie: 10W30 (3/1) is better than 10W40 (4/1)or 5W30 (6/1).

- The recommendation for my Healey down to 5C (41F) is 20W40 or 20W50.

I run 20W50 (2.5/1 viscosity ratio) in my Healey.

John, BN4

02-08-2003, 06:47 AM
Hi guys.

I know conditions in the UK are somewhat different to Hawaii,(Is there still that awful pinapple packing factory next to the airport?),But I have found that the best oil to use in a Healey engine is the Penrite 20/50. It seems be a little thicker (not a very technical term I'm afraid), than more modern oils. I think they also do a 10/60 but I don't have any experience of that particular oil, although in theory it should be better for the more "elderly", i.e worn out, engine.
Cheers graemlins/savewave.gif graemlins/england.gif graemlins/savewave.gif

Gary Pope
02-09-2003, 01:38 PM
Laste week I switched to 10/30 Castrol "Hard Driving" and I really don't like it. When cold the oil pressure is way up high at 70psi but after about 10 miles or so and engine is at normal temp .. the oil pressure starts to go down at an alarming rate even when driving you can see the oil needle start to decline backwards. At idle it is about 10psi a little to close to the bottom. My previous oil would fluctuate from cold 60psi to hot 25psi at idle. The 10/30 seams to really thin out quickly.

I can't wait to get the thicker oil back in.

02-09-2003, 02:07 PM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by MGTF1250Dave:
These polymers break down over time resulting in engine deposits, viscosity and thermall breakdown. ...
The temperature range in Hawaii is small, about 60 deg F minimum over night low in winter to 95 deg F maximum day time high in summer. <hr></blockquote>

Dave, unless you're planning to leave the oil in for an extended lenght of time, the breaking down will not be a problem. Modern oils will not deteriorate that fast. If you're changing the oil on a 3K or even 5K schedule I don't think you have anything to worry about.

Your comment about ambient temps is right to the point. The advantage of multi-weight oils is quicker lubrication on start-up and extended temp range, neither of which is particularly critical in your situation.

I think you could use either multi or single weight without harm, as long as you don't have oil pressure issues, like Gary mentioned.

02-11-2003, 07:12 PM
Mahalo (thanks) for the input. Alan, the Dole pineapple cannery is closed, but the building is now a shopping center. We are cleaning up the "industrial/junkyard" look of the drive from the airport to Honolulu, but still have some work to do.

Silky pointed out that single weight oils very basic. I found that most major oil companies list the specifications for their various products on the websites. In addition to viscosity, other factors should be considered such as viscosity index, flash point, % sulfated ash and % zinc.

Multi weight motor oils generally have better performance specification than the single weight oils. Probably market driven since car manufacturers specify multi weight motor oils.

Many websites confirmed that Silky was correct that motor oil will last well beyond 3000 mile oil change interval that Jiffylube and others hype.

My revised opinion is now that I will use a 20W50 motor oil.

Safety Fast,