Question 1

It says to add it at oil change . Is it Before or after the oil change?

Accepted Answer

The short answer is use this before the oil change at about one full gas tank away from the your oil change. After you run your full tank of gas almost empty, refill it, then change your oil ASAP. 
The long answer is due to modern engine designs with direct injection and high compression ratio, the gas injected into the combustion chamber will blow-by the piston rings causing the gas to dilute your oil. The nice thing is that it would probably not matter if you do a lot of driving at high way speeds for more than 1 hour each week as the blow-by gas will be recirculated into your combustion chamber to get burned of. If you do a lot of short trips and surface street driving, the engine never gets to operating temperature to burn off the excess blow-by gas, in such case, make god help your engine if it's in there for 5000 miles (oil is cheap, don't do 10,000 miles) or so. Again, the chemists at Shell Gas put a lot of cleaning agents into their gasoline and using Shell gas probably will not hurt your engine. The chemists at Gumout do not put again claims on their product, so be safe rather than sorry and use before oil change. Hope that helps.

Question 2

What’s the difference between the each gum out products? Like what’s the difference between the “all in one “ and the “regane”?

Accepted Answer

All in one works better than Regane.
It can be seen by looking at the price difference.

Question 3

my car gas  tank has 11 gallons, how many liquid  can put on it ?

Accepted Answer

I'd say 1/2 to the full bottle.  It will just clean the carbon faster.  It doesn't hurt at all to run it that concentrated.

Question 4

Can any of these gumout fuel system cleaners help with the egr valve? it has a good bit of carbon buildup.

Accepted Answer

I would first check with a GOOD auto mechanic to verify what you are claiming. If as you say, that the EGR valve has a carbon build up, is it possible to remove it for cleaning? What does your mechanic recommend? I myself use the ALL-IN ONE fuel cleaner to keep my fuel injectors & fuel system clean ONCE a month though the mfgr says every 3000 miles.

ASIN	B01BM5XWU6
Best Sellers Rank	#1,398 in Automotive ( See Top 100 in Automotive ) #11 in Fuel System Cleaners
Brand Name	Gumout
Contains Liquid Contents?	Yes
Customer Reviews	4.6 4.6 out of 5 stars (493)
Global Trade Identification Number	00071948901063, 30071948100160
Included Components	All-in-One Fuel System Cleaner (1)
Item Form	Liquid
Item Type Name	Fuel System Cleaner
Item Volume	10 Fluid Ounces
Manufacturer	Gumout
Material Features	Eco-Friendly
Material Type Free	Chlorine Free
Model Number	510016
Number of Items	1
Part Number	800001366
Scent	Unscented
Size	10 Fl Oz (Pack of 1)
Specific Uses For Product	Fuel System
Surface Recommendation	valves
UPC	071948901063
Unit Count	10.0 Fluid Ounces

All-in-One Complete Fuel System Cleaner

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