OIL TEST
Page 35
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Having got the vehicle and track organised for the aerodynamic test, we decided to push the comparison a little further and investigate the claims of improved fuel consumption with lower viscosity semisynthetic engine oil. The theory is that with thinner oil less power is required to turn the engine or push the lubricant around. This leaves more available to propel the vehicle.
The effect of lower viscosity oil is more closely related to engine speed than vehicle speed. We tested this by doing both acceleration and constant speed runs—first with a normal 15W/40 and then with Shell's semisynthetic Myrina TX 10W/30. Both runs were at 88km/h—the first with same 15W/40 engine oil used in the main trials, and the second using a 10W/30. Acceleration runs were made from a standing start to the point at which the speed limiter cut the power.
Unfortunately, the weather turned against us between the two runs. On the first (calibration) run with 15W/40 oil there was a light wind and a dry track. By the time the oil was changed and the truck was back up to operating temperature the wind had picked up (gusting to 52km/h) and it started to rain during the run.
With the thinner engine oil the fuel consumption went up by 2% but, given the deterioration in the weather, we reckon that was a creditable result.
As Myrina TX is a SHPD (CCMC D5) oil it has the longest drain period—around 40,000 to 45,000krn in most engines.
Myrina TX has a list price of 21.29 per litre against 21.19 for the nonsynthetic 15W/40 Myrina M (also CCMC D5). With such a small price difference (this is due for review soon), the most marginal improvement in fuel economy will give a payback.
While we could not quantify this on our test, the results gave us the
• feeling that
this saving would be (36.54) attainable. We will carry out more tests soon and will return to this subject.