Do I believe the evidence or the dealer?

[dulecki]

In the interest of changing only one variable at a time, I'm going to put off the oil change for a couple of weeks.

You see, following the excellent instructions I found here at PriusChat, I decided to check the cabin air filter this morning before heading off to get the oil changed at dealer number 2.

I found somewhere around two cups of dog food on it, along with other scrap material! Apparently, some mouse or rodent has been busy... Unfortunately, I didn't take a picture, although I did show it off to everyone in the family

I've now got a new filter (since the old one was chewed up a bit) and removed most of the dog food... some of it spilled off the filter, so I've still got to clean that out. I picked up a flexible crevice tool at a local vacuum cleaner shop... just the thing to reach into those narrow spaces, I think I'll post a review of it after I'm done getting the last of the dog food.

In the meantime, I gassed up today and in the ten miles since then, I'm averaging 49MPG... easily a 10MPG increase in my book. I'll see what it all looks like when I'm done, but this just might be a silver bullet....

Points to ponder...

1. How long has that stuff been there? If it's since the check the dealership did a bit ago, that rodent's been really, really active. If it's been there since September, why didn't the dealer notice when I brought the vehicle in to get the poor MPG checked? It takes me all of 90 seconds to check it now...

2. If that's the culprit, then why the sudden dropoff in mileage back in September? I suspect the oil change added to it... the paperwork shows that they put 4 quarts in, and the dipstick shows pretty full as of this morning. I'll double check that as well... a little later on today.

3. At both oil changes, they did a multi-point courtesy check. Do they actually have a checklist, and can I get a copy? I'll have to ask them... it would be interesting to know what exactly went on.

More news when I get it, but I suddenly have the feeling I could join the 50+ club here shortly...

[a priori]

An you've got me wondering who may have set up camp in my air filter . . .

You've GOT to post pictures.

[fruzzetti]

Originally Posted by FL_Prius_Driver

I should not because the running viscosity (30) is the same. The cold, starting viscosity (5W or 10W) determines how fast the engine gets lubricated on startup (I am sure you knew this already, so this really is not aimed at you).

In the case of the OP, if the dealer put in the wrong oil, it could have been really wrong rather than just slightly different. It looks like the OP knows what he is doing so I expect we will find out before too long.

what, like 90-weight gear grease?

(important)
I'm so amazed to read this thread. I don't have anything to contribute, but that I've also reflected upon many recurrences of the exact same symptoms you describe.

Here's what happens to me (not important, but detailed):

(1) take vehicle in for scheduled maintenance

(2) car gets shockingly worse gas mileage on the way out

I've encountered this numerous times, and every time I start thinking about Microsoft and the term "planned obsolescence" and it just drives me nuts but there's no hard evidence of anything other than a suspicion.

Moreover, I wouldn't -actually- suspect planned obsolescence (nobody would want their own brand vehicle (or any vehicle they service) to leave the shop with noticeably worse performance, ruling out all but the least deliberate of motive.

(important again)
I never could figure out what manner of accidental mis-calibration could cause such a dramatic drop. But then, my tires were always under-inflated coming out of the dealership.

It does seem strange to me, now that I'm seeing others experience it.

However, I'm a mathematician; many of you should have heard the phrase "correlation does not imply causation" and I'm sure plenty of people can describe dealer trips after which their mileage remains unchanged, and I can certainly describe times my mileage has taken a nose dive for reasons that are certainly NOT dealer-related.

~ dan ~

I conclude that if there's a causal relationship, it's a serious, but accidental, cause.

[FL_Prius_Driver]

Originally Posted by fruzzetti

what, like 90-weight gear grease?

Yeah, that would really do it. I do not know if anyone has run a controlled experiment of seeing what the MPG changes are depending how what viscosity oils are put in. If someone has I would really like to know about it.

[richlaz]

I also got poorer mileage after the 5000 mile dealer oil change on my 07, but put it down to the colder weather, since I do not keep very accurate mileage records. However, they did tell me that there was an upgrade to the computer that they did. I would guess that upgrade would apply to all 07's. I wonder if that could have caused your problem.

[NROhioPruis]

I have a 2007 and had it since Sept. I got a 5000 mile oil change at a local Quick Change; due to the fact that my dealership is a 40 min drive each way. i have not noticed a MPG drop due to this, but have due to the weather dropping. i will be blocking the grill later this week. if you use synthetic oil can you go to 7500 miles? i know the manual states 5000, but isn't that with regular oil? What are the benefits to using synthetic with such a small motor? if i do go back to reg oil, should I change it after 3000 miles or stay with 5000?

Thanks

[fruzzetti]

I know for a regular vehicle with a full-time ICE (like my Mustang) it can benefit from ultra-light 0W-30 synthetics, so that you have oil pressure the instant you start cranking the engine.

I don't see how it would benefit the Prius, because it does all its stopping and starting after it's warmed up, when the oil is at its higher viscosity number.

~ dan ~

[FL_Prius_Driver]

Originally Posted by NROhioPruis

I have a 2007 and had it since Sept. I got a 5000 mile oil change at a local Quick Change; due to the fact that my dealership is a 40 min drive each way. i have not noticed a MPG drop due to this, but have due to the weather dropping. i will be blocking the grill later this week. if you use synthetic oil can you go to 7500 miles? i know the manual states 5000, but isn't that with regular oil? What are the benefits to using synthetic with such a small motor? if i do go back to reg oil, should I change it after 3000 miles or stay with 5000?

Thanks

Whenever you talk about extended oil change intervals, get ready for a lot of comments on invalidating the warranty. It does not invalidate your warranty but you should know exactly what oil is being put into your car if you do so. 0W-30 or 5W-30 synthetic are the common choices for extended intervals. In very cold weather 0W-20 has been used by some.

Right now my program is to change the oil at 10,000 mile intervals. I use AMSOIL Synthetic 0W-30 and have the oil tested to ensure it is still in very good condition for extended intervals.

As a last note, The 2001 Prius (with the exact same engine as a 2007) has the Toyota Oil Change interval being 7500 miles, so what you are wanting to do was standard practice. The reason for the change to 5000 had nothing to do with the Prius, but due to problems Toyota had with big engines and bad oil and the Prius is an innocent victim of that.

If you want more info, search for posts by jayman. You do not need to change at 3000 miles, you are just wasting oil by doing that. For 5000 mile intervals, either synthetic or regular will work fine. It is the longer intervals (10,000 or more miles) that synthetic is the better choice.

[Rxmxsh]

That's amazing! My MPG's have dropped a little too, but I figured it was mostly due to tempreture. How do I check my air cabin filter?

I'll admit - I haven't searched yet, but I am about to!

Edit - using John's site - it's the filter right behind the glove box, no?

[dulecki]

You're correct. It's the one behind the lower glove box.