Mazda 2.5L Skyactive DI sluggish

My lovely wife has put almost 60k miles on our 2014 Mazda 6 with the 2.5L Skyactive 4. I don't drive it much but this weekend I drove it 2 hours on the interstate and noticed it is down on power pretty significantly. Cruising at 70mph any pressure on the gas forces a downshift to gain any speed at all. Driving in traffic it feels almost scary slow, and it sure didn't when new. Thinking maybe I was just used to my Mustang I clicked over to the avg mpg. Ouch. Long term average is down to 28 from 32+. Something's definitely up.

I change the oil like clockwork, always Mobil 1, and check the other general maintenance stuff, but haven't really turned a wrench on it. I'm thinking at 60k it may be time for plugs (haven't checked the manual's service interval yet.) I'm also aware of DI engines having some serious deposit issues. So what have you guys seen with the 2.5L engines? What's involved in checking for deposits, or better yet cleaning them? Can it be DIY'd? I remember some discussion on this a while back, but the engines were new enough it was still mostly speculation. Does anyone have real world experience with this yet?

Is it still under warranty?

The extended warranty, yes, but I think the original was 36k. Why?

Then it's not your problem. Take it to the dealership and explain what's going on.

Ah. I might take that route, but our dealer has an absolutely godawful service department. Honestly, the only time they've touched this car it was for a TPS issue, and I had to print out the factory issue documents and take them to them personally in order to get them to do anything besides scratch their ass and chase their tail.

Then take it to a different dealer.

First thing before all of that, how is it driven?

Give it a good Italian tune up, all modern DI engines need a good hard flogging to get the carbon deposits out, even if it's not DI it helps.

JtspellS wrote: First thing before all of that, how is it driven? Give it a good Italian tune up, all modern DI engines need a good hard flogging to get the carbon deposits out, even if it's not DI it helps.

That makes it worse, not better. What causes the massive deposits is oil blowby condensing/carbonizing on the hot valves and such. Blowby increases with load, heat increases with extended load.

The cleanest DI engines I see are putted around at idle most of the time.

Dealer or after when its not under warranty do a chinese water torture or the good old fashoned method of put a small vac line from the closest behind the throttle body, run inside the car with a little aquarium ball valve with the other end sticking in a gallon of water, get on the highway with the valve shut off then when your up to speed open it up and let it suck in that gallon. When its empyy shut off the valve and keep driving another 30 miles or so to boil off the water that may have gotten into the oil. Good old steam clean

Keith Tanner wrote: Then take it to a different dealer.

next closest one is 2 hours drive.

chiodos wrote: Dealer or after when its not under warranty do a chinese water torture or the good old fashoned method of put a small vac line from the closest behind the throttle body, run inside the car with a little aquarium ball valve with the other end sticking in a gallon of water, get on the highway with the valve shut off then when your up to speed open it up and let it suck in that gallon. When its empyy shut off the valve and keep driving another 30 miles or so to boil off the water that may have gotten into the oil. Good old steam clean

This entered my mind, but with the stupid high cylinder pressures and super-heated valves, I'm not sure I want to be the first one to try this. Seems like a hand grenade waiting to happen.

Could try one of the intake cleaning kits. I know fords DI motors recomend cleaning it every 20-25k.

CRC makes an intake valve cleaner for DI engines that might be worth checking out.

That CRC looks like it might be worth a shot. At least if it makes a difference I have some evidence of the problem.

This may or may not be related at all, I don't know how much the 2.0 and the 2.5 skyactiv engines have in common (mine is a 2012 in a 3).

First, different gas seems to make a bigger difference than I would have thought. For example, the engine seems to have less power when I use Speedway, and gas mileage goes down noticeably when I use Shell (all 87 octane). It seems to like Mobil, Citgo, and BP the best. Note that this is all subjective, and even I'm not totally convinced that it's not all in my head.

Second, I changed the battery about 5 months ago. This reset stuff like my average MPG readout, and I've heard that the car's computer will learn how you drive and adapt to it (?). I don't really know what that means, but my car seems different after the battery was unhooked. Again, this could be in my head.

So I guess I'm saying try unhooking the battery and using different gas.

FWIW, I have ~50,000 miles on mine.

I used the CRC Intake Valve cleaner on my last oil change with the 2013 Focus, GDI engine. Mileage increased from 36 to 38 average in mixed driving. That and increasing tire pressures slightly to 40 psi were the only changes to the car. Gasoline fill-ups are at the same station. Not sure if it was the CRC, but it appears to have made a positive impact!