Here is a quote from someone that I copied for reference. It explains things pretty well:
"Meguiar's Gold Class wash is 4:1 water to shampoo in foam gun (estimate).
Since Gemini suggested that we have a thread dedicated to foam gun ratios, I figured I'd volunteer my time for it (hey I'm on summer break and I love helping everyone at DB). However, I'll only be offering what I know for my Gilmour Foamaster II #95QGFMR.
The particular Gilmour model I have has a multi-ratio dial with 5 mixing head settings. All these settings/specifications can be seen at the Gilmour website for your own personal reference.
The most common used setting, at least for me anyways, has always been the C setting with an output volume of 4 oz./gal. In most cases car wash shampoos suggest having 1 oz of car wash shampoo added for every gallon of water. Initially you might ask, why not just keep it simple and use the A setting where its output volume is 1 oz./gal? The answer is the foam gun is not capable of sucking such a viscous liquid through its siphon tube. Now I can not attest to whether this is true or not but I don't dare try it myself. However, there is the exception with some of those cheaper car wash shampoos in which they are pretty watery (and probably not great car wash shampoos altogether).
There's also the B setting (2 oz./gal.) which can be used as well but just remember that your shampoo mixture may still be too viscous for the foam gun to handle. One nice thing about the B setting though is that you will not be required to refill as often as you would as the C, D, or E settings.
Since I mentioned the D and E settings, I will say that these settings are definitely not ideal. Their output flow, 6 oz./gal. and 12 oz./gal. respectively, is just too fast and will require a lot of refilling! For me, these are simply not an option almost all the time but perhaps maybe it is for others. I won't even bother with the E setting as it's just not practical for me but I will mention the one occasion in which the D setting is actually useful later. Anyway, on to the hard numbers!
We'll start with the most common dilution, 1 oz of car wash shampoo to 1 gallon of water. The 95GQFMR is a quart container which is the equivalent of 32 oz. At the C setting, we have an output flow of 4 oz./gal. Now in essence, we want 1 oz of that 4 oz./gal. flow to be car wash shampoo and in order to achieve that, we must have a 3:1 ratio in the 95GFQFMR container. So how do you do that? It's pretty simple. You add 8 oz of car wash shampoo and 24 oz of water so that your ratio comes out to 3:1. So what if you want to use the B setting? Sure, that can be done. Your ratio will then effectively be 2:2 or 1:1 and you will be adding 16 oz of car wash shampoo and 16 oz of water. The only concern with using the B setting is whether or not your mixed solution will be soluble enough to be sucked up through the siphon tube and provide the proper volume output. Of course as I mentioned before, the B setting will require less refilling than using the C setting which is nice.
Ok, so what about car wash shampoos such as Chemical Guys Citrus Wash & Gloss? Well, they have 2 different dilutions for separate applications. There is one dilution that is ideal for the weekly wash in which 1/2 oz of CWG is required for every 2 gallons of water or 1/4 oz of CWG for every gallon of water. There's also the paint cleanser dilution which is 2 oz of CWG for every gallon of water.
In order to achieve the proper dilution for CWG as a weekly wash, we need 1/4 oz of car wash shampoo for every gallon of water. Now this gets a little tricky with the 95QGFMR and I may lose you in its translation. Since our previous dilutions have been 1 oz of car wash shampoo to 1 gallon of water, we need to figure out what setting we'll be using before we dive further into the numbers.
If we want to go with the most common C setting, the short answer is we divide by 4. Now if we divide our original 8 oz of car wash shampoo by 4, that gives us 2 oz of car wash shampoo and leaves us with the remaining 30 oz of the 95QGFMR to be filled with water. To fully understand how this calculates out, we have to remember that at the C setting we are outputting at a rate of 4 oz./gal and we want 1/4 oz./gal. If you think about it, 2 oz of car wash shampoo to 30 oz of water is simply 30:2 or 15:1. However, we are still at a ratio to 1 and what we really want is to 1/4 or .25 in order to understand the numbers in a simpler form. To keep it fairly simple, we divide both sides of the ratio (15:1) by 4 which gives us 3.75:.25. Well what do you know, these two numbers add up to a total of 4, meaning 4 oz, which also meets our requirement of 4 oz./gal. output flow.
So what if you want to use the B setting? It's pretty simple. Just use 4 oz of CWG and 28 oz of water, with the ratios working out as follows (keep in mind these are all equivalents): 28:4 -> 14:2 -> 7:1 -> 3.5:.5. -> 1.75:.25.
Okay, now that's out of the way. What if you want to use it as a paintwork cleanser? So it's 2 oz of car wash shampoo to 1 gallon of water. Ok, simple enough but it's doubtful that you'll be using the B setting for this one. Essentially if you do decide to use the B setting you'll have to fill the entire container with solid CWG, non-diluted. As I mentioned before, the 95GQFMR will not be likely to successfully suck this viscous liquid through it's siphon tube. So C setting it is and it's simple. You need 2 oz of car wash shampoo for every gallon of water and at the C setting we have an output flow of 4 oz./gal. Essentially, we just need a 1:1 ratio here, 16 oz of CWG and 16 oz of water. Now if that mixture may be too viscous still (I haven't tried it myself yet), this would probably be the only occasion in which the D setting would be feasible, IMO. At the D setting we have an output flow of 6 oz./gal. which would mean that in order to achieve a 2 oz of car wash shampoo for every gallon of water, we'd need a 2:1 ratio, which roughly comes out to 11 oz of CWG and 21 oz of water (the ratio isn't exactly 2:1).
Ok so that was a lot of reading (if some of you actually read it all) but below you will find the short and sweet version for your reference. I'll continue to add to it if need be. I hope my English was structured well enough to understand, LoL. Either way, I hope it helps out some of the fellow foam gun users who are still new to its dilution ratios or just need some refreshing of their memory. Enjoy!
Gilmour Foamaster II #95GQFMR
Any car wash soap at 1 oz per gallon of water
C setting - 8 oz of any car wash soap + 24 oz of water
B setting - 16 oz of any car wash soap + 16 oz of water
Chemical Guys Citrus Wash & Gloss at 1/4 oz per gallon of water (weekly wash), also applies to Citrus Wash & Clear and Maxi Suds II
C setting - 2 oz of CWG/CWC/MSII + 30 oz of water
B setting - 4 oz of CWG/CWC/MSII + 28 oz of water
Chemical Guys Citrus Wash & Gloss at 2 oz per gallon of water (paintwork cleanser)
C setting - 16 oz of CWG + 16 oz of water
D setting - 11 oz CWG + 21 oz of water
Detailer's Pride Xtreme Foam at .4 oz per gallon of water
C setting - 3.2 oz of DPXF + 28.8 oz of water
B setting - 6.4 oz of DPXF + 25.6 oz of water
Detailer's Pride Xtreme Foam at .5 oz per gallon of water (for simplicity and/or rounder numbers)
C setting - 4 oz of DPXF + 28 oz of water
B setting - 8 oz of DPXF + 24 oz of water"
