I'm running a series of tests of an oil additive to try and measure the effect of engine operation. This is based upon measuring the fuel consumption of the engine at idle during warm-up and idle during cool-down. So far, I've only been looking at warm-up fuel burn.
The protocol is to start the car and shift into "N" a few seconds after the engine is running on its own. I'm using our 1.5L, NHW11 which shares the same engine as the NHW20 and AutoEnginuity to record the data:
The key data are: coolant temperature, engine rpm, ignition timing and mass air flow (MAF). There are four useful records:
#2 - 0W-20, Mobil 1, 8k service miles, 2 quarts were drained including filter
#3 - 5W-30, Mobil 1, 0 service miles, 2.5 quarts were added
#4 - 5W-30, Mobil 1, ~150 service miles
#5 - 5W-30, Mobil 1, ~150 service miles, added 8 oz additive and 8 oz of 0W-20 to rinse container
One unexpected result is two tests starting under 12C changed the ignition timing from 10 to 5 degrees about 660 seconds into the test. In contrast, two tests were the starting temperatures above 20C kept the ignition at 10 degrees. This suggests at colder temperatures the spark is retarded which would increase the exhaust gas temperature because less work is extracted from expansion stroke. But we are interested in the oil additive.
The next charts compare the new oil versus the same oil with the oil additive:
There was an offset in the spark reduction to 10 degrees offset due to the 11C difference in starting temperature. Furthermore, as the engine ran, the lower heat loss due to warmer ambient temperature means then engine warmed up a little faster.
Increasing the Y-scale, show nearly identical MAF profiles except at the end where the virgin oil suggests a slightly lower fuel consumption compared to the same oil treated:
However, the oil additive instructions report that the additive takes a while to coat the metal surfaces and it suspends gunk and varnish:
"If used when you change your oil, simply add with any premium oil. If used between oil changes, add to engine at least 1,000 miles before your next oil change. This will ensure sufficient time for boundary layer formation and bonding. Add directly to crankcase when the engine is warm, then run engine approximately five minutes."
"This treatment will remove sludge and varnish from your engine. When used in engines with over 100,000 miles, change the oil and replace the oil filter after 1,000 miles to eliminate these contaminants from your engine." - additive instructions on side of box
To investigate this further, the time line was offset so the first ICE rpm drop starts at the same time reference:
The plateau of the ICE coolant occurs when the thermostat opens up allowing the rest of the coolant to flow through the engine block. Once all coolant is at the same temperature, warm-up continues.
Changing the Y-axis scale, we see the ignition advance change occurs concurrent with the engine rpm reduction:
Again, increasing the Y-scale, the MAF lines are all but on top of each other:
There is no evidence that treating the oil had an effect during a cold-start, warm-up. This raises a question of whether or not we could detect any difference in oil friction effects.
To test the test, we compared the 0W-20, 8k service miles to the virgin, 5W-30 oil. Changing the time scale to align inflection points, we find a consistent gap between the used and new oil during warm-up:
This data set provided ~2,400 samples showing the lower fuel consuming 0W-20 with 8k service miles versus the stock, 5W-30 with 0 service miles.
Mapping the relative ratios we find the 0W-20 has about a 2% reduction in fuel consumption versus new 5W-30:
Good Prius friend, David Kelly, found a reference that 0W-20 has about 2% lower internal friction than 5W-30.
The oil additive instructions require 1,000 service miles before a second oil change to remove the varnish and gunk it releases from older engines. At that point, it should have coated the moving parts with a low friction layer. But 1,000 miles exceeds the tank capacity of our NHW11 so I'll have to run gas reference tests before and after each tank. Otherwise, there is a risk of measuring a change in winter-summer gas energy content and not the oil additive effect. Also, I didn't add the oil to a 'hot' engine so I may use the second oil change to add the remaining 8 oz.
Bob Wilson