I have always run 30w in my manual push mowers per owners manual. I only had about 10oz of 30w left so topped off with another 10 oz. of 15w40. I was surprised how much further I went on the tank of gas. Usually I have to fill up 2-3 times. This time I filled up twice but the tank was much fuller when I stopped at my normal time to fill up. I guessing the amount of gas I used was 20-30% less. Plus, the grass was taller and thicker than usual because of rains this week. Just surprising and thought I'd share
Metter "mileage" with 15w40 and 30w mix
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Sorry to burst your bubble, but that's impossible.
Funny thing. For years I have proclaimed the advantage of using lighter engine oils in OPE. Obviously, a 15W40 oil requires more energy to move around in a splash lubricated engine, and burns more fuel to do so. About three weeks ago, I set out to prove this.
My lawn vac has a 4.5 hp Tecumseh engine. It had EXXON 5W30 dino oil in it. I filled the gas tank carefully, noted the time, and cranked it up. It ran almost exactly 45 minutes and stopped. I drained the hot oil out, giving it a long time to drain. I refilled with Pennzoil 15W40 oil, and refilled the fuel tank. Cranked it back up and waited. At about the 40 minute mark, I begin to pay close attention, as I was sure it was about time for the 15W40 to make the tank run dry. But, no. It continued to run, and run and run. It passed 45 minutes and continued to run. Finally, at 49 minutes it ran out.
I could not understand this. I am going to repeat this test using new 5W30 (the 5w30 I drained had about 20 hours on it).
My lawn vac has a 4.5 hp Tecumseh engine. It had EXXON 5W30 dino oil in it. I filled the gas tank carefully, noted the time, and cranked it up. It ran almost exactly 45 minutes and stopped. I drained the hot oil out, giving it a long time to drain. I refilled with Pennzoil 15W40 oil, and refilled the fuel tank. Cranked it back up and waited. At about the 40 minute mark, I begin to pay close attention, as I was sure it was about time for the 15W40 to make the tank run dry. But, no. It continued to run, and run and run. It passed 45 minutes and continued to run. Finally, at 49 minutes it ran out.
I could not understand this. I am going to repeat this test using new 5W30 (the 5w30 I drained had about 20 hours on it).
JTK
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Cool observations! I think there's just too many variables that will effect fuel consumption in small OPE. With a sump of just ounces of oil, I don't think you'd be able to measure a consistent difference between a 20wt or a 50wt.
Joel
Joel
Not sure where my reply went???
When you added the oil to an already hot engine, you pre heated the oil. Hot oil is thinner than cold oil.
Run your test in reverse order, viscosity wise, and see what happens.
When you added the oil to an already hot engine, you pre heated the oil. Hot oil is thinner than cold oil.
Run your test in reverse order, viscosity wise, and see what happens.
Hey, Bill, look closely at your posting of my posting. Your reply is in about the middle of my entry. Anyway, the engine had over an hour to cool down. I have made many entries expressing my opinion that thinner oil gives more power and less fuel consumption because of the drag of the oil slinger. That lawn vac now has about 45 hours on it, and I think it is time to be changed over to Mobil 1 5W30. I am about out of pre SM Mobil 1 so I think I will use M1 SM and save my remaing old M1 for my 2000 model Honda engine mower. I'll run one more test on the 15W40 this coming week , and then do a test on the 5W30 M1.
I agree that one should EXPECT more power/economy with a thinner oil. It just takes more than 1 test to be definitive.
Something else to keep in mind is that someones 40 weight may be closer to 35, while someone elses may be closer to 45. They do round to the nearest number.
I know in the early spring, (temps <50), my mower sure starts a lot easier with 10w30 than 15w40. It's a matter of 2-4 pulls vs 8-10. Warmer weather, it's 2. Maybe I should change out that 6 year old spark plug?
Something else to keep in mind is that someones 40 weight may be closer to 35, while someone elses may be closer to 45. They do round to the nearest number.
I know in the early spring, (temps <50), my mower sure starts a lot easier with 10w30 than 15w40. It's a matter of 2-4 pulls vs 8-10. Warmer weather, it's 2. Maybe I should change out that 6 year old spark plug?
How would the oil's viscosity affect how many pulls it takes to start a mower? How hard it is to pull? Maybe, but I think other factors outweigh oil thickness for that. How it runs when it finally starts? Sure.
Maybe the plastic gas tank warmed up from the first run, and expanded. Maybe the air going into the engine warmed up by 10 degrees, and the oil temperature followed, making the oil 50% thinner. Warmer air is also lighter so there'd be less drag on the blades. But it's an interesting observation and worth testing.
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