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Old 06-15-2021, 09:04 AM   #1 (permalink)
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Priuses(?) on the Highway

Iím window shopping for and daydreaming about cars on Kijiji yet again. I want to get extreme MPG and will modify a car heavily to do so. Wanted a TDI but donít like the maintenance costs, plus people sell ones with more than 400k km on the odometer for $3000+ which is absurd to me. My other idea is to get a bone stock Ď93 Civic CX hatch Iíve found and mod it out.

Then again, Iíve started seeing some pretty good Gen 2 Priuses(Prii?), and Iíd like to know what I should expect for MPG if I were to get one. My commute is more than 75% highway, and most of my travels are on the highway as well. A highway-focused machine is best for me. Iíve read that hybrids arenít very useful on the highway and something like a TDI is better suited for high speed fuel efficiency. Is that the case? As far as I can tell, Prius Gen 2 owners manage 45-50MPG on the highway, which doesnít amaze me.

A battery replacement probably helps these quite a bit, right? Definitely far from being a new car.

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Old 06-15-2021, 09:20 AM   #2 (permalink)
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It depends on how fast you want to drive.
On the highway the battery does not get exercised much so its condition would not make a difference. Speed is everything for MPG; the slower the better.

An old Civic with a manual gearbox could well beat the Prius. The more you mod, the bigger the difference; the Prius is already quite optimal and relatively heavy, your options are limited there.

I would still go with the Prius because it is a lot safer and easier to drive.
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Old 06-15-2021, 09:55 AM   #3 (permalink)
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I get nearly that mileage in my Spyder lol
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Old 06-15-2021, 11:31 AM   #4 (permalink)
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There thing with an older Gen 2 Prius is the potential maintenance and repair costs in the near future.

The battery is going to need to be replaced son and is going to cost more than $1,600. I have not heard of anyone having any luck with cheap aftermarket batteries. And you can "recondition" your old battery yourself, but again with limited results. Thw only aftermarket battery that I'd trust is the one from NewPriusBatteries. But for the price you're not that far off from an OEM battery especially if you don't want to deal with parting out your old battery modules.

There is talk of a LiFePO4 replacement battery in the works that many of the real Prius gurus over on Prius chat have confirmed works as intended in all sorts of road tests. I do have my doubts though.

Another potential expensive repair is the brake controller.

And yet another problem is oil consumption. I do thoroughly believe that if the oil were changed at least every 6 months or 5,000 miles these engines would last over half a million miles. But people go by the yearly oil change and then end up with oil consumption problems down the line, which in turn kills the catalytic converter.
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Old 06-15-2021, 11:57 AM   #5 (permalink)
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I've had a 2005 and 2009 Prius and a 2003 and 2014 TDI Jetta wagons.

The Prius would do 50 mpg at 70 mph. Increase speed to 80 mph and the fuel economy drops to around 40 mpg. Slow down to 60 mph and the fuel economy goes up to about 60 mpg

The old 2003 Jetta Wagon TDI 5 speed would do about 53 mpg at 70 mph, 50 mpg at 75 mph and 45 at 80 mph. I never really ran extended periods at 55 - 60 mph with it.

The 2014 TDI does a disappointing 40 - 42 mpg at 65 - 70 mph.
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Old 06-15-2021, 12:41 PM   #6 (permalink)
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Quote:
Originally Posted by Isaac Zachary View Post
And yet another problem is oil consumption. I do thoroughly believe that if the oil were changed at least every 6 months or 5,000 miles these engines would last over half a million miles. But people go by the yearly oil change and then end up with oil consumption problems down the line, which in turn kills the catalytic converter.
I don't know how much of a unique problem this is with Prius, but I doubt oil change interval has much to do with it. I've checked my oil condition with yearly changes and it was still well within spec.

The unique thing about the Prius is that it's designed to run the engine at high load continuously, which puts more strain on everything. If excessive wear is a problem with the Prius, I would suspect the cause is high loads and thin oil (0w20).
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Old 06-15-2021, 01:52 PM   #7 (permalink)
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I don't know how much of a unique problem this is with Prius, but I doubt oil change interval has much to do with it. I've checked my oil condition with yearly changes and it was still well within spec.

The unique thing about the Prius is that it's designed to run the engine at high load continuously, which puts more strain on everything. If excessive wear is a problem with the Prius, I would suspect the cause is high loads and thin oil (0w20).
It's much more complicated than just "engine runs harder", but frequent oil changes seem to prevent the problem all together.

First, these cars have low tension rings. Add to that the oil relief passages behind the oil control ring are small. When those passages and the oil control ring get clogged the piston now turns into an oil pump that pumps oil up into the cylinder.

One solution is to change the compression rings out for high tension rings. That way they always force oil through the oil control rings and relief passages as they scrape down and not up into the cylinder. But then there goes your efficiency because now there's more friction.

Another solution is to take the pistons and drill out the relief passages so that it's less likely for them to clog.

Or just change your pistons and rings every 100,000 miles or so.

But the easiest solution is to just change the oil by the manufacturer's true recommendation. Oil gets dirty and degrades over time and miles. So keeping fresh oil in the engine prevents deposits which prevents oil relief passages and control rings from clogging.

However, it seems like a lot of people change their oil yearly, if that. So they go 15,000 miles or so between oil changes when the manufacturer recommends yearly or every 10,000 miles whichever comes first under optimal conditions. But the thing is that very very few drive under optimal conditions. Optimal conditions are summer weather flat road trip conditions. If you drive short distances, over mountain passes, in stop and go traffic, you're a trailer OR in cold weather the real oil change recommendation is now every 5,000 miles or 6 months, whichever comes first.

The problem is that there is now an epidemic of oil burning Toyotas with less than 200,000 miles because hardly anybody changes their oil by the manufacturer's true recommendation for the driving conditions. And at the same time there's a group of people that have nearly half a million miles or more on their Prius or other Toyota because they've changed the oil faithfully every 5,000 miles (or 6 months, whichever comes first).
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Old 06-15-2021, 02:54 PM   #8 (permalink)
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Mild oil use doesn't bother me. That's when I start getting the Tuesday oil change special at Jiffy Lube for $25 and have them add a quart between changes for free. I'd tolerate a quart every 1000 miles, but any worse than that and it begins to get annoying.
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Old 06-15-2021, 03:33 PM   #9 (permalink)
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I can't quite remember the number, but I do believe a couple quarts every 5,000 miles is about the limit according to the manufacturer.

Personally I prefer to not have to add oil between oil changes. A quart every 1,000 miles more than doubles the oil I need to buy. At as much as 30,000 miles per year of be buying 30 quarts more than necessary per year. Not to mention oil consumption wreaks havoc on the catalytic converter.
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Old 06-15-2021, 04:05 PM   #10 (permalink)
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Quote:
Originally Posted by JSH View Post
The Prius would do 50 mpg at 70 mph. Increase speed to 80 mph and the fuel economy drops to around 40 mpg. Slow down to 60 mph and the fuel economy goes up to about 60 mpg.
This is pretty much what I get as well with my 2004.

My sister had an ALH and I worked on it several times. I would not go that route...

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