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160k miles, now best MPG is down to 19 mpg

Started by jimmyducati, February 04, 2018, 05:02:31 PM

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jimmyducati

I just turned 160k miles and my mpg is down to 19mpg max, down from 26 driving the same route for 2 years now. Car drives flawlessly, tires inflated appropriately.

I change the oil with 5w20 Pennzoil platinum synthetic using the oil life reading as an indicator. PTU oil is changed every other oil change with Amsiol sever gear 75/140. RDU oil is original. Air filter is clean, 3" downpipes, no cats and no CEL's indicating an issue with the o2 sensors, witch are less than 2 years old.

I drive 80 miles round trip for word everyday, so this drop in MPG's is a significant hit to the wallet!

Any known things that can cause this dip in mpgs other than winter fuel playing a factor?
2010 White SHO w/two tone interior
2005 Ducati 999s  (the daily ridder)
1998 Ducati 916  (the beauty queen)
1995 Ducati 900ss (the track terror)
1978 Harley Davidson Shovelhead

griggs95

RDU doesn't for Run Don't Undertake lol. Seriously though, why the neglect in the rdu and overkill with the ptu? Rdu is much easier to change imo, and throw Amsoil in that as well. Nice daily driver btw.

-Does the car use much oil?
-Did it all of a sudden drop or is this a gradual loss in mpg's?
2011 pp: lms 91 tune - ppe downs w/ kitties - Amsoiled myself all around - gapped 30 sp plugs - enthused driver, nervous passengers - aem drop in dry filter.

SHOdded

Wow, that is a BIG drop.  x2 on what griggs95 said.  Change out the RDU fluid as soon as possible, hopefully it has little to no metal shavings in there.  If pasty/dirty looking, R&R repeatedly with "cheapo" fluid like Walmart SuperTech until it stays clean, then final fill with fluid brand of choice.

Check the intercooler for crud buildup, clean the MAF sensors.

Spark plugs might be getting long in the tooth, I assume you have changed them once already by now?  You can easily gain back 2-3 mpg if the plugs are worn enough.

Can you scope the valves to see if carbon buildup might be an issue here?  There isn't really an effective dropin FI cleaner that will help.  A GDI induction service would be my recommendation, it can also help gain back a good amount of mileage.

Has the coolant ever been serviced?  Should be on 3rd set of coolant by now.

Any issues with the AC compressor?  That can cause drag.  Brake calipers and slide pins too.

All the usual things with any car:  alignment, tire tread/pressure, removal of excess/unnecessary "cargo", ...

And of course pull codes, just in case.
2007 Ford Edge SEL, Powerstop F/R Brake Kit, TXT LED 6000K Lo & Hi Beams, W16W LED Reverse Bulbs, 3BSpec 2.5w Map Lights, 5W Cree rear dome lights, 5W Cree cargo light, DTBL LED Taillights

If tuned:  Take note of the strategy code as you return to stock (including 3 bar MAP to 2 bar MAP) -> take car in & get it serviced -> check strategy code when you get car back -> have tuner update your tune if the strategy code has changed -> reload tune -> ENJOY!

jimmyducati

The economy dropped off gradually over the last 10-15k miles, drivability however has been flawless as usual.
Second round for the coolant, due for a third now, was going to add some water wetter the next go round but it has never had an issue with heat. The plugs are about 20k old, properly gapped for the 4x+ 93 tune. Brakes are the 14.4" "top cop" z34 package, about 5k miles old and in perfect order.

Ill go through it this week after the coolant flush and change plugs, clean the MAF and double check the emissions equipment and toss in some fresh plugs for good measure. I didn't think the RDU was a problem in these cars, guess that will get the cheapo flush with amsoil in the end. Flushing the PTU every other oil change may be overkill, but with a drain plug and fill tube installed, its so easy to do.

Does the intake valve cleaning cost a lot of $$? If its not to much, that will be the next step if they are bad.
2010 White SHO w/two tone interior
2005 Ducati 999s  (the daily ridder)
1998 Ducati 916  (the beauty queen)
1995 Ducati 900ss (the track terror)
1978 Harley Davidson Shovelhead

pmezo33

Post your fuel trims.  Short term and long term.

SHOdded

Usually a GDI induction service is between 150-200$ depending on where you get it done.  Not sure if there is a DIY kit out there to do so.

Plugs are sp534 or something else?  Assuming you run 93 due to the tune and it is top tier.  Try cleaning the MAP sensors and IAT sensor with MAF cleaner first.  Check intercooler buildup.  If it has buildup, may need a new pcv valve and separator.

May be time for o2 sensors perhaps, per pmezzo's post ...
2007 Ford Edge SEL, Powerstop F/R Brake Kit, TXT LED 6000K Lo & Hi Beams, W16W LED Reverse Bulbs, 3BSpec 2.5w Map Lights, 5W Cree rear dome lights, 5W Cree cargo light, DTBL LED Taillights

If tuned:  Take note of the strategy code as you return to stock (including 3 bar MAP to 2 bar MAP) -> take car in & get it serviced -> check strategy code when you get car back -> have tuner update your tune if the strategy code has changed -> reload tune -> ENJOY!

jimmyducati

GDI induction service, is that the BG cleaning? I am going to run a scope into the intake tomorrow and look at the valves, if they have buildup I'm going to get a media blaster and compressor and pull the intake and clean them with walnuts. I don't have much faith/confidence in the chemical cleaning and with the age of my turbos/engine I don't want to risk deposits making their way through the system.

Plugs are sp534, and Shell 93 from the same gas station is all I purchase. I have a new set of O2 sensors in the box if i need them, but I'm not getting any codes for them currently.

Thanks for all the suggestions so far, great place this forum is!!
2010 White SHO w/two tone interior
2005 Ducati 999s  (the daily ridder)
1998 Ducati 916  (the beauty queen)
1995 Ducati 900ss (the track terror)
1978 Harley Davidson Shovelhead

SHOdded

Yes, BG, but Valvoline also has a pro GDI system, I think ZSHO had his dealer use it last time ...  Of course if you can media blast them, so much the better!

Once you post fuel trims, we will have a better idea if we need to look at the O2s or not.  That's why I find the OBD devices VERY useful, saves a lot of parts swapping & headache.
2007 Ford Edge SEL, Powerstop F/R Brake Kit, TXT LED 6000K Lo & Hi Beams, W16W LED Reverse Bulbs, 3BSpec 2.5w Map Lights, 5W Cree rear dome lights, 5W Cree cargo light, DTBL LED Taillights

If tuned:  Take note of the strategy code as you return to stock (including 3 bar MAP to 2 bar MAP) -> take car in & get it serviced -> check strategy code when you get car back -> have tuner update your tune if the strategy code has changed -> reload tune -> ENJOY!

jimmyducati

Ive got an hour drive home tonight and another back tomorrow morning, so ill post them as soon as I can.
2010 White SHO w/two tone interior
2005 Ducati 999s  (the daily ridder)
1998 Ducati 916  (the beauty queen)
1995 Ducati 900ss (the track terror)
1978 Harley Davidson Shovelhead

pmezo33

Quote from: SHOdded on February 05, 2018, 05:48:27 PM
Yes, BG, but Valvoline also has a pro GDI system, I think ZSHO had his dealer use it last time ...  Of course if you can media blast them, so much the better!

Once you post fuel trims, we will have a better idea if we need to look at the O2s or not.  That's why I find the OBD devices VERY useful, saves a lot of parts swapping & headache.

Agreed.  Diagnosing and replacing is always less expensive than just throwing parts at a problem and hoping it fixes it.  The computer is there to help. 

ZSHO

#10
I think you mentioned you installed new brakes! Double Check the Caliper slide pins which are common to cause the brakes to drag some.  Z


2013 Performance Package SHO| Livernois Custom Methanol Tune|3-Bar Map|Reische-170-Stat|Full Race Tial-10psi BOV in Black|PPE-Gloss Black Hot Pipes|EPP Dual Intake in Gloss Black|PPE Catted DP|Corsa Sport Cat Back Exhaust|H&R Sport-Springs|CFM Performance Billet Valve Cover Breather In Gloss Black|Llumar 20%Ceramic window Tint|MSD Ignition Coils in Black|Extreme Roof Spoiler|Redline Fluids all around|Gearhead Intercooler|First-SHO With Direct Port Alky-VP-M1-100%-Methanol Injection|LMS-Custom-Dyno-Tuned @ 415whp-465wtq| Best Trap Speed of 115.54 mph|

jimmyducati

Data logs for your viewing enjoyment. I'm really bad at figuring out what i need to include, so I included ALOT...
2010 White SHO w/two tone interior
2005 Ducati 999s  (the daily ridder)
1998 Ducati 916  (the beauty queen)
1995 Ducati 900ss (the track terror)
1978 Harley Davidson Shovelhead

jimmyducati

Quote from: ZSHO on February 05, 2018, 06:38:00 PM
I think you mentioned you installed new brakes! Double Check the Caliper slide pins which are common to cause the brakes to drag some.  Z

Brakes were One of the first things I checked, along with tire pressures, trans fill level and having the alignment checked. Alignment was slightly out and needed a tie rod end, fixed both same day.
2010 White SHO w/two tone interior
2005 Ducati 999s  (the daily ridder)
1998 Ducati 916  (the beauty queen)
1995 Ducati 900ss (the track terror)
1978 Harley Davidson Shovelhead