Motor Oil Analysis from Range Rover 4.6 Engines

This investigation was sparked by three primary things: I discovered varnish or sludge on our Rovers' dip sticks; a coworker swears by AMSOIL and Mobil 1 synthetic oils; and a friend thought that Royal Purple was the best and that AMSOIL was a "snake oil" pyramid scheme. So, I aim to find out which of these full synthetic oils is the best for our vehicles and if the full synthetic oils are actually better than the low-cost conventional Walmart and AutoZone oils that I have been using.

Erin bought her 2000 Land Rover Range Rover 4.6 HSE in March of 2007 on Saint Patrick's Day with 55000 miles on it. I bought my 2000 Land Rover Range Rover 4.6 Rhino on July 4th of 2007 with 55000 miles on it. I have been using Walmart or AutoZone 10W-40 conventional oil and STP oil filters from 55000-85000 miles on the HSE and from 55000-80000 on the Rhino. I changed the oil immediately after purchase and I have been changing the oil every 5000 miles even though the manual allows for a longer interval. Both vehicles have a black and brown coating of varnish or sludge on the dip sticks that seems to be getting worse over time.

I converted the HSE to AMSOIL on October 6 of 2009 at 85000 miles. I drained the old oil, took an oil sample, replaced the filter with another STP filter, and filled it with new AutoZone 10W-40 oil again. I added AMSOIL engine flush to the oil and ran the car between 1500rpm and 2000rpm for 20 minutes in neutral to clean out some of the crap built up in the engine. Then I drained the flush oil and replaced the STP filter with an AMSOIL oil filter. Then I filled it with AMSOIL 10W-40 and put a new air filter on. Finally, I put two 16-ounce cans of Sea Foam in the fuel tank and filled it with gasoline. It is running noticeably smoother now. I was really surprised, but I noticed a difference right away. Erin commented on it the next day when she drove it. Apparently you can use Sea Foam as an engine flush also, but I did not discover that until after I bought the AMSOIL engine flush.

I converted the Rhino to Royal Purple on November 25 of 2009 at 80000 miles. I drained the old oil, took an oil sample, replaced the filter with another STP filter, and filled it with new AutoZone 10W-40 oil again. I added AMSOIL engine flush to the oil and ran the car between 1500rpm and 2000rpm for 20 minutes in neutral to clean out some of the crap built up in the engine. Then I drained the flush oil and replaced the STP filter with an AMSOIL oil filter. Then I filled it with Royal Purple 10W-40 and put a new air filter on. Finally, I put two 16-ounce cans of Sea Foam in the fuel tank and filled it with gasoline. It is running noticeably smoother just like the HSE.

I used different oils in subsequent oil changes to gather more data. Oil Analyzers Inc. performed all of the oil analysis for me. I bought the prepaid postage oil test kits through AMSOIL's website at the same time I bought AMSOIL oil and filters, which was very convenient. All of my samples listed the grade of oil, date, mileage, and unit, but not the lube manufacturer to guarantee unbiased test results.

The first thing to notice is the similarity between sample #1 for both engines. This first sample period used the same AutoZone lube for the same mileage to establish a meaningful baseline. Both samples show a 100C viscosity of 10.1, which indicates that the SAE 40 has degraded to an SAE 30. An SAE 40 oil should have viscosity between 12.5 and 16.3. In fact, all of the values are very close except for silicon contamination in the 4.6. The samples indicate that the engines are in very similar condition and performing in a similar manner. I should be able to compare oil samples from each vehicle with the exception of silicon contamination.

My conclusions are listed after the oil analysis results table.

Oil Analysis Results For The HSE

[an error occurred while processing this directive]

Oil Analysis Results For The Rhino

[an error occurred while processing this directive]

Conclusions for 10W-40

The Auto Zone conventional oil degraded and performs like an SAE 30 instead of an SAE 40 after 5000 miles, which means that protection is seriously reduced. The TBN is extremely low, which means that this oil is not capable of neutralizing much more acid and degradation would likely accelerate soon. The Royal Purple oil also degraded to below an SAE 40 viscosity, but not as bad as the conventional oil. Most of the wear metals are reduced compared to the conventional oil and the total wear metal count is about half, but the engine experienced more highway miles than normal during this period because of a 3200 mile cross country trip. The AMSOIL degraded to just below an SAE 40. The TBN and additive metals were high and the "High Zinc Formula" they claim seems to be accurate. Unfortunately, the wear metals increased, but I think this is a result of the increased silicon contamination and far fewer highway miles for this period. The AMSOIL definitely had the most severe service of all 10W-40 oils tested given my knowledge of how the vehicle was operated. The viscosity of the Castrol held up well and was still within SAE 40 range. Mobil 1 High Mileage experienced 1700 highway miles with a 4000lb trailer and an additional 800 or so with no trailer. The viscosity held up well in the SAE 40 range.

Picking a winner out of these oils is much more difficult than I originally anticipated. There was a lot a variability in the service life of each oil tested even though they all received almost exactly 5000 miles. The miles/day on each oil and the number of highway or trailer miles varied considerably. I will definitely not use cheap conventional oil again because of the sludge, varnish, and measurable inferior performance. I would be hesitant to use Royal Purple because it had the greatest viscosity reduction of the synthetics while also having the least severe service life. I would have no problem using AMSOIL, Castrol Syntec, or Mobil 1 in the future.

Conclusions for 5W-40

I decided to test two different 5W-40 oils for the winter because of our move to Syracuse, NY. I tested Mobil 1 Turbo Diesel Truck and Shell Rotella T6 in our two Rovers. Both Rovers experienced similar driving conditions during a similar time frame. Both of these 5W-40 oils are excellent. They both held up better, in terms of final viscosity, than many of the full-synthetic 10W-40 oils I tested, which is very surprising given the greater difference between cold and hot viscosity ratings. Both oils had a final viscosity well within the range of an SAE 40 and both had a TBN high enough to indicate they had some life left in them. I would have no problem using either oil in the future, but Shell Rotella T6 is clearly the best oil I tested. Its viscosity held up better than every 10W-40 oil I tested and better than Mobil 1 Turbo Diesel Truck 5W-40 despite lots of short trips and winter idling while clearing snow and ice. Better still, Shell Rotella T6 is available in gallon jugs for cheaper than most of the other oils I tested. It is usually between $20 and $24 per gallon, which works out to between $5 and $6 per quart. I will be using Shell Rotella T6 from now on.

Motor Oil Analysis from a Buell 1125 Engine

I really got curious about motorcycle oils after I started testing oils in the Rovers. I found some excellent background information on motorcycle oils: Sport Rider August 2003 Oils Well That Ends Well, Part 1, Sport Rider October 2003 Oils Well That Ends Well, Part 2, and AMSOIL June 2009 A Study of Motorcycle Oils Second Edition. Many of the oil test results match up between the two studies despite the 6 year difference. Also, AMSOIL does not win every one of the test categories in their study. Therefore, I think these two observations lend a lot of validity to the AMSOIL study and I am inclined to believe the published results about all of the oils tested in both studies. However, I want to independently test at least 2-3 oils that appear in the AMSOIL study to see how my real-world results compare.

I found another great article called All About Motor Oil. It covers many motor oil topics in great detail and the author strongly advocates using synthetic commercial-certified (Diesel) oils or conventional commercial-certified (Diesel) oils in motorcycles because of the additive packages and cost. The newest API standard (SM) oils are not necessarily good for high-performance motorcycle engines or older engine designs because of a shift in the additives allowed. I would argue that many of the motorcycle-specific motor oils are excellent and that a "Diesel" oil is not required. The author's goal seems to be finding the most cost effective protection and not necessarily finding the best protection that money can buy.

I broke the bike in according to the guidance in the owner's manual. It was torture, but I actually stayed under the RPM limits for the mileages specified. I was very happy after I did the first service and I could really unload on it. An SAE 50 oil should have viscosity between 16.3 and 21.9. My conclusions are after the oil analysis results table.

Oil Analysis Results For The Buell

[an error occurred while processing this directive]