Calculating cost savings of owning fuel efficient second car for commute?

[Isaac Zachary]

Originally Posted by redpoint5

Good point, I was going to mention oil changes...

I'd probably only do 2 oil changes per year assuming about 26,000 miles per year. Highway miles are easy, and I've gone 13,000 miles between changes in the Prius and oil analysis always said it had more life left.

I buy synthetic when it's on sale and stock up. Same with filters. One nice thing is my CBR600 motorcycle uses the same filter as my Acura TSX.

I know a lot of people who (claim to) get away with over 10,000 mile oil changes and can get (or claim to get) 150,000 to perhaps even 200,000 miles or more out of an engine that way without any major problems. But personally I've also seen way too many cars not make it near that far, and the obvious reason was trying to change the oil every 10,000 miles or more (clogged and gummed up oil passages, oil control rings, even the oil pan pitted or eaten through from the acidity). And I've also seen engines with 200,000, 300,000, 400,000 and even 700,000 miles on them and didn't so much as burn a quart of oil between oil changes. So people can squak and bark all they want about how they can do way more miles than what the manual says, but I'm still sticking to the manual.

Sure, an oil change analisys can help. And if you want to send in an analisys every oil change, fine. But is it really easier, cheaper and as trustworthy as just changing the oil on time?

IMO, if you really want to keep the car for as long as possible I recommend going by the most often oil change intraval in the owner's manual, usually 3,000 to 5,000 miles or 3 to 6 months (depends on car and whatever comes first). Unless you drive correctly for the longer oil interchange (6,000 to 10,000 miles). By that I mean, drive exclusively cruising down the highway for over 30 miles per trip, don't idle, don't drive in cold weather, don't drive in the mountains, don't pull a trailer or put on a luggage box, and don't cold start more than once a day. And no, starting your engine in 100°F 40°C weather after parking all day at work does not count as a warm start.

Oil is way cheaper than an engine rebuild or a new engine. Sure, the engineers that know way more about these engines are trying to control us into following their recomendations. But I think I'm going to side with the engineers this time.

[redpoint5]

I had the analysis just for my own curiosity, not really intending to justify or modify my oil change intervals. I change the oil once a year whether it's needed or not.

That said, I've never had engine problems from any vehicle I've owned. They're built too good these days to give any problems even for those who miss the recommended change interval.

Anyhow, throwing an oil changing party this weekend. Probably do 5 or so vehicles.

[cRiPpLe_rOoStEr]

Having an oil analysis might be worth, and eventually give you some clue about engine damage if you compare the amount of some metallic residues between oil changes for instance.

[redpoint5]

Originally Posted by cRiPpLe_rOoStEr

Having an oil analysis might be worth, and eventually give you some clue about engine damage if you compare the amount of some metallic residues between oil changes for instance.

I always paid extra and got info on remaining life of the wear inhibitors.

Here's the thread where I contributed yearly updates... until I stopped.

https://ecomodder.com/forum/showthre...nge-20705.html

[Isaac Zachary]

I wonder if you have to pay extra to test for the detergents.

The Prius I got with over 200,000 miles on it apparently has gummed up rings. Although there are a lot of things in the design that contribute this common failure on Toyota engines, from what I can find the problem isn't an issue if you just change the oil every 5,000 miles or sooner which allows the oil to keep those oil control rings clean.

[redpoint5]

Originally Posted by Isaac Zachary

I wonder if you have to pay extra to test for the detergents.

The Prius I got with over 200,000 miles on it apparently has gummed up rings. Although there are a lot of things in the design that contribute this common failure on Toyota engines, from what I can find the problem isn't an issue if you just change the oil every 5,000 miles or sooner which allows the oil to keep those oil control rings clean.

Not saying I don't believe it, but I'd want to know the method of action that extending change intervals causing gummed up rings or oil passages.

My understanding was the hydrocarbon chains break up as oil is used, making it less viscous over time.

I'm not familiar with the role of detergents to keep the engine clean, though I know it helps with maintaining fuel injection components in gasoline. I've never had an issue with a fuel system either, and I buy the cheapest gas I can find.

[Isaac Zachary]

Oil has detergents to clean and suspend carbon and dirt in the oil, which then gets removed when the oil is removed. Clean oil, like a sink full of soapy water, does a good job at keeping things clean, kind of like washing your dishes. But once it gets too much carbon in it, like too much grime from dishes, it stops holding onto the carbon and dirt which then start forming deposits, like when your dishes start coming out of the sink looking worse than when you put them in there.

The piston rings are a tough one to lubricate and clean because they are near the combustion event and have to deal with hot blow by gases and no real way to pump oil in to make it flow. The best that can be done is to have them scrape the oil and sort of force it into the oil control ring and out the oil relief passages in the piston. Once the oil stops cleaning there at that high heat, low flow area, stuff starts to build up. Once clogged there goes the engine as oil can't flow and lubricate properly.

[cRiPpLe_rOoStEr]

Originally Posted by redpoint5

My understanding was the hydrocarbon chains break up as oil is used, making it less viscous over time.

This may explain in part the high oil consumption of some engines, as some broken-down hydrocarbon chains might become much more volatile. Remember the so-called catalytic cracking of kerosene, resorted by some refineries to make high-octane gasoline?

[Piotrsko]

You could probably triple dose it with something like seafoam and synthetic oil, but it also takes out the clearance avoiding sludge in the bearings and other spinny things.

[Isaac Zachary]

Originally Posted by cRiPpLe_rOoStEr

This may explain in part the high oil consumption of some engines, as some broken-down hydrocarbon chains might become much more volatile. Remember the so-called catalytic cracking of kerosene, resorted by some refineries to make high-octane gasoline?

From what I understand it's the viscosity index modifiers that break down first and cause it to become thinner. Basically 5W-30 becomes 5W-20, 5W-15 and eventually just plane 5W once the viscosity index modifiers have broken down. Then as contaminates fill the oil it starts to eventually thicken again.

The base stock oil is the last to break down and change. If it changed too much it wouldn't be recyclable.