I actually can believe what you are experiencing but could be for a couple reasons. I have hit 28mpg once myself. However, temp was right about 0 degrees Fahrenheit and was driving though icy passes. That is the only time I have hit that low.
I have a 2018 touring with 43k miles. Live in northeast Washington state. I used to calculate the mpg by hand when fueling on long trips like people suggest but found the calculation by the car was within 0.5mpg as long as I reset when changing to hv so rely on its calculation.
Cold definitely affects the mpg as does speed, amount of heat used, tires. Lowest 28 as above. When new in summer driving 800 mile round trip with some city driving, freeway at 75mph averaged about 44-45mpg. Summers now on freeway about 41-43 mpg affected by speed (going 65-80mph). Winter trips typically about 35-38 mpg. All through mountain passes. Commonly taking the car skiing right now driving majority of way 50-60mph. Averaging 46.7mpg.(that excludes time driving in electric when I reset meter- I drive down my hill all in electric, up the steepest part of the ski hill electric and repeat in opposite order on way home with the middle flatter part in gas).
First thing I would consider from your report that you can fix regardless of driving style. Do fully charge the battery or at least have it 3/4charged even if you are going to drive in HV. Have seen up to a 5mpg difference (usually about 2-3) driving on depleted battery vs full.
2) heat is a huge player. When I drive EV I get about 40 mile range in winter, wife gets about 28. Difference is I set the heat at 67. She sets it at 86. Similarly I get higher mpg in hybrid then her. My understanding is unless you have the Canadian edition you are using straight resistance heating regardless of engine running or not. Not very efficient heat. (Canadian has heat pump that is slightly better)
3) tires matter. 1 see about a 1-2mpg difference (and similar decrease in EV range) as soon as we put on snow tires regardless of temp. Similarly under inflated tires has cost us 1-2 mpg as well at 1 time)
4) mode matters a little - Econ seems to get 1mpg more for me
5) finally though if you are not cranking the heat and getting those type of mpg, need to get it looked at. I have had a couple times that driving on trips, battery 3/4 full in hybrid on the 55mpg roads that I got down to mid 30mpg. At that time, no matter what I did with the regen the charge going down hills would barely be below the white neutral line. Seemed like something was wrong with battery or regen system. Dealer could never figure out why but has happened 3 times. Don’t know rules for you state and probably not as generous as for Washington, but here it follows California laws. Battery has 150k warranty and regen system 100k (I believe on the latter) transfers to any subsequent owner. I would recommend you get it checked by a dealer that knows the clarity (only one guy knows it at our shop and he LOVES it so we get good care. Nobody else there has a clue)
5) finally, if the other owner abused your battery it could be the issue. Ie if they never charged it and drive it purely hybrid. If driving up fairly steep hills with depleted battery, based on the way ours drives coming up our hill in that condition, I suspect you can force it to deep cycle and damage the battery. When we were looking, dealer had one on lot that they NEVER charged and initially did not know how to. Drove horrible in hybrid. When we drove one that was getting charged, was beautiful. Both <200 miles on them.
Hope something in there helps.
(also separate thought. Clarity
PHEV is the best car I have ever owned by miles. (2 prior camrys, Honda Odyssey, 2015 leaf and cheaper cars for comparison). Not perfect but really nice. However, would not buy new again for one reason. Never crash tested so insurance premiums are ridiculously high. I am pretty sure it is safe but apparently insurance does not think the same. (New price after rebates/no sales tax was about the same as paying 24k with taxes for something else)
