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The other time I asked my mechanic, are my tyres about needing to be changed?

He said, naw, another 8000 miles. After driving 7000 miles, I asked another mechanic who again said, long way to go.

Does hyper-miling reduce the stress on the treads of my tires and ultimately the question - does hypermiling reduce the stress on engine oil?

I included the description of my tyres to illustrate the possible effects of hypermiling. I have a manual stick-shift. I don't hypermile compulsively like hybrid car drivers. I hypermile by giving adequate distance between myself and the truck/car in front of me to allow me to slow down. I accelerate gradually. I cruise to red traffic lights. And I do drive a lot across states to get 40 - 45 mpg out of a stick-shift Honda Civic.

So, after 7000 miles, my engine oil is still viscous and golden in colour but a little dirtier. Could I say that the molecular integrity of my engine oil can be correlated to its viscosity and goldenness? Should I change the engine oil as the mechanic recommends (so he could earn the $40 minus the oil) or should I wait till the oil has lost most of its golden-ness and viscosity.

I mean, I used to have an automatic Ford Escort whose oil would turn completely dark and watery after 5000 miles.

What is the science behind the degradation of engine oil that refutes or supports my correlating viscosity/colour to its lubrication integrity? Do you think hypermiling reduces stress on my engine and engine oil?

I need to add that I am using normal non-synthetic oil. And my car doesn't have air-cond.

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From what I read everything you do is admirable.So far not addressed is tyre pressure. Correct pressure = lower mpg. and no overheating(of tyres) issues –  mike Apr 18 at 10:22

3 Answers 3

up vote 2 down vote accepted

I'm no expert on the subject so I'd take this with a grain of salt, but here's the thing with oil.

The common belief is that when your oil starts to go darker then it's time for a change, but that isn't exactly true, as it actually means that the oil has been doing its secondary job of removing particles and dirt from the combustion chamber and suspended it within itself (which is later filtered through the oil filter before reentering the chamber).

The fact that the oil maintains a more natural color just means that it is picking up less dirt as it travels through the engine, which could just mean the air filter in the new car is better than the one on the Ford Escort, thus less dirt is coming into the engine in the first place.

About the hyper-miling, it is likely that the more you do it, the less dirt comes into the engine as engine only rotates because of the transmission being hooked up to the wheels rotating in the ground, but [probably] no gas consumption is actually occurring and less explosions in the chamber are leaving even less residues behind, although I doubt that with your way of driving hyper-miling is making an actual difference in the oil. I think the engine of the new car is just better, filtering air better and creating a cleaner burn inside the chamber.

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First, the driving style that you described certainly places less stress on both tires and engine oil. You avoid hard braking and hard acceleration. This puts less wear on the tires than someone who brakes and accelerates hard. End of story. By avoiding hard acceleration, you put less heat into your engine than someone who accelerates at full throttle, which could potentially slow the degradation of the engine oil.

With your tires, it is very simple to determine when they need to be replaced by measuring the remaining tread depth. With the engine oil, it's not as simple. The "clean" appearance of the oil does not necessarily mean that the oil is "fresh." If you really needed to know the condition of your used oil, you could take a sample and send it out for oil analysis. This will give you the information you need to determine whether the oil can safely be used beyond the manufacturer's recommended change interval.

However, it's seldom worthwhile to stretch oil change intervals. An oil change is cheap insurance against larger engine problems. One can get VERY technical about oils, debating the merits of synthetic vs. conventional, one brand vs. another, etc.; but the simple mantra holds true: new oil is better than old oil, which is better than no oil.

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Consumer reports article does not seem to agree with your statement " ... it's seldom worthwhile to stretch oil change intervals. An oil change is cheap insurance against larger engine problems." It says, do not change the oil unnecessarily. –  Cynthia Avishegnath Oct 21 '13 at 17:42
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How do they define "necessary"? As I said, if you really care about getting it right, send the oil out for professional analysis. If you want to be safe, follow the manufacturer's recommendations. –  mac Oct 21 '13 at 19:46
    
No ... someone should understand the breakdown process at the molecular level and let us know rather than flailing our arms wildly. –  Cynthia Avishegnath Oct 22 '13 at 0:47
    
Replacing oil is dirt cheap; determining if you need to costs a lot more, in terms of lab work, than just replacing it. –  R.. Oct 22 '13 at 3:11
    
Yep - always replace the oil. It is so cheap, and the alternative so expensive, that it makes sense. –  Rory Alsop Oct 22 '13 at 7:52

Concerning your oil question - the best way to tell if you can delay your oil changes is to have the oil tested.

http://www.blackstone-labs.com/

That is a great company to have it tested. They can do an analysis and tell you exactly how much impurities are in it and whether the oil still has more life in it or not. Again though, if your goal is just to save money, the extra $25 for the test might not be worth it.

Like everyone else said, you can't tell unless you test. The color of oil is no indication of whether you need it changed or not.

https://www.youtube.com/watch?v=oi_J4SZUlSo

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