I have a large vehicle parts database that i am changing the format of so is a big job. Im trying to add a button to semi automate it on a couple of standalone pages. Ive been working on this for several hours and tried everything i can find online but it still doesnt work. I must be missing something simple, can anyone help?

sample url so you can see the variables are working is

update.php?old_model=Celsior+UCF21+4.0+1UZ-FE&new_model=Celsior+UCF21&engine=4.0+1UZ-FE

code i have is

<?php

global $wpdb;

$old_model = $_GET["old_model"];
$new_model = $_GET["new_model"];
$engine = $_GET["engine"];

 //These arent required, only there to confirm variables are populated   
echo 'Old Model ' . $old_model . '<br>'; 
echo 'New Model ' . $new_model . '<br>';
echo 'New Engine ' . $engine . '<br>';


$table_name = $wpdb->prefix.'wpe6_ymm';
 $data_update = array('model' => $new_model ,'engine' => $engine);
 $data_where = array('model' => $old_model);
$wpdb->update($table_name , $data_update, $data_where);

?>

expecting the database to update with the new values but it doesnt