I am going to do the 1st of the horse syringe drain & replace the reservoir later this week. 3 bottles of Prestone full synthetic power steering fluid for Asian (on label as compatible with Honda) vehicles (36 ounces total). The 2007 Honda Pilot hold 1.2 quarts of power steering fluid. Mine looks like it's never been changed ever and starting to sound like it's never been changed ever too.
The way I figure it, the syringe method will dilute to 50% new / 50% old for each set of 3 12 oz bottles you switch out. 2nd set of 3 12 oz bottles = 75% new / 25% old, 3rd set of 3 12 oz bottles = 87.5% new / 12.5% old, 4th set = 92.5% new / 6.25% old, and final 5th set = 96.88% new / 3.12% old.
Actually, that's not really accurate but is lazy math as after the 1st bottle from then on, I will be replacing in a ratio of 12 oz 100% new to 12 oz 100% old only on the very first bottle. The 2nd bottle will be adding 12oz 100% new and removing 12oz fluid pre-mixed at a ratio of 12oz new/ 24oz old / 3 = 4oz new / 8 oz old so I will confoundingly be tossing 4 oz new fluid in the pre-mix. That means after 2nd bottle, I'll have 20 oz new and 16 oz old. 3rd bottle I'll be tossing about 6.6 oz new and 5.3 oz old and have 25.4 oz new and 10.7 oz old which works out about to the 70% new 30% old ratio.
Still pretty dirty at 70% new / 30% old? Would adding bottles 4, 5, & 6 help much? 4th bottle works out to toss about 8.5 oz new / 3.6 old tossed and you add in 12 oz new for 28.9 oz new / 7.1 oz old (80% new 20% old). 5th bottle = 31.3 oz new / 4.73 old (87% new / 13% old). And the final 6th bottle would be 33 oz new / 3 oz old (92% new / 8% old) So probably doing that for 6 bottles is more than enough, I think, at least for me the improvement in doing the 6th bottle after the 5th is minimal but it's about equivalent to the YouTube video posted earlier and others that say they wound up having to do 2 flushes so I'll do 6 bottles but no more although I will do 3 bottles per year of the synthetic PSF for Asian vehicles from here on out just to play it safe. I really want to get switched to the sufficiently synthetic with 6 bottles starting out though as it oxidizes much less readily than the natural.
So, changing out only 6 bottles using the horse syringe method is good for me. The current price is $10.97 at the local Walmart so to reduce the amount of dirty fluid using this method is $66 plus tax. It's very expensive, but much cheaper than a new power steering pump and the labour for the mechanical clutzes like me that are hesitant to do it themselves.